Finch - Slow bird, easy to get in Journey mode, otherwise kind of random chance to acquire. Good for defending yourself early game, but kind of a dumb AI, and will run circles around enemies a lot.
Slime - Solid beginning minion, though requires a ridiculous amount of luck (I think 1/2000 chance to drop from slimes??) best chance to get this is going to come from King Slimes minions or the slime rain prior. Either way, not a priority, though really good late game for AFK farming for gold with a Greedy Ring (will only do 1 damage per hit, giving massive payout)
Flinx - Best choice early game, should honestly just shoot straight for this as you'll also need the robe early on. Very good for protecting yourself, and surprisingly decent against flyers. They kind of cling to whatever they hit, just kind of bouncing off of them. Can get stuck on walls and doors fairly easily though, but most staves early game will do the same.
Hornet - A flying minion, usually a bonus because they won't just randomly jump at flying enemies and waste most of their summon time. Will also inflict a poison debuff, shooting a stinger at enemies. Solid choice, may be worth using at least one of just for the poison.
Fire Imp - Same as hornet basically. Used to be much the inferior choice, but is fairly consistent now. Will inflict the On Fire! debuff, and the projectiles are a bit faster than the Hornet staff. Useless against enemies in the water though, and I hear they don't deal damage to enemies that cant be inflicted with the On Fire! debuff? I can't confirm or deny this one (help me out in the replies!) It can glitch out while shooting an enemy offscreen though, firing shots over and over like a machine gun and inflicting massive damage!
Vampire Frog - Kind of annoying to grind, but very worth. Recently buffed to deal damage with tongue attack and just coming into contact with enemies. Will end up doing the most damage, in almost all scenarios, but suffers the same fate of most ground minions as it can struggle against flyers. They have a nice jump though, and can jump from the top of lava and water to hit most things. I'd say the biggest drawback to this summon is that if you're flying or jumping high, they will just fly with you instead of attacking anything around you.
Spiders - Solid minion, easily available early on in hardmode. Will inflict a venom debuff, and cling to the enemy that they are hitting until they die or you drift too far away from them. Problem is without background walls, it may be kind of hard for them to connect with the enemies as they use background walls for most of their movement. Stronger than most other available staves at this point in the game, but heavily reliant on walls, and too many spiders will make the invincibility frames so constant that you cannot deal other damage.
Blades - Very smart AI, hovers above your character, attacks your enemies, and returns above your head. They ignore a massive 25 armor on all enemies, making up for their abysmal summon damage. Very fast hitters however, stacking very well with whips that apply summon tag damage (like Durendal or Snapthorn). Fast and precise, but not very good with Firecracker or against enemies with too much health or armor. No invincibility frames, which will help you deal more damage with your whips and other sources. Can also attack through walls if used properly.
Pirates - RIDICULOUS damage and no invincibility frames, making them a very nice choice in the proper situation. Gets stuck on walls and sometimes just go AWOL?? I swear some of them just run away after a while, or just get stuck and cant figure out how to fix it. They are phenomenal for AFK farming, blood moons, and Eternia Crystals though. Can get stuck a lot around the base and when mining. They will reposition with a flying parrot if you go too far though, which can help with the stuck problem. They also poop all over the place, like ALL over the place. Honestly a very fun summon.
Sanguine Bats - VERY smart and attacks almost never miss. Will float above you, attack the enemy, and return to their position. Attacks even faster than the blades. Can attack through walls in the right situation. You won't see any massive numbers with this summon, but the sheer consistency will make up for it tenfold. Can handle Duke Fishron with just Hallowed Armor, helping to get powerful staves early on. They have HUGE knockback, and will certainly increase your survivability in general play. I am very biased towards this weapon if you couldn't tell.
Optic Staff (Mini Twins) - Honestly, this staff used to be one of the best. Now unfortunately a little overrated. Best against things like Destroyer and segmented enemies, where one of the eyes charges through and hits multiple times, but can miss a lot. Does have the bonus of being a flying summon however, and can be consistent in general play.
Tempest Staff (Sharknados and Sharkrons) - Got a decent buff recently. Can be very strong in a lot of situations. Floating sharknados are now faster, chasing enemies more and dealing more damaage with the actual tornado. They also fire more frequently and the sharkrons travel faster as well. Summon a bunch of these guys and you can see some massive damage numbers. Can help kill Plantera with ease, annihilating his health if you smack him with durendal then firecracker, and kite him into the barrage of sharks. Used to be a very lack luster reward from a very challenging boss, now quite the opposite! Can replace Sanguine Staff efffectively.
Pygmy Staff (little tiki dudes) - Also got a decent buff. Can be very worth using, I'm just not a fan personally. Will throw spears that cause the VENOM debuff though, making having at least 1 a very viable option, not so much if you are using Venom Flasks on your whip though. Decent staff for directly after Plantera.
Desert Tiger - VERY fun summon, and incredibly smart AI. Doesn't care about walls, pouncing through them and defending you as much as possible. Downside is it's only one summon, so it can't defend you from all angles at once. Upside is, it's only one summon, so it's damage is huge, and makes the firecracker one of your best single target options for a long time! Definitely worth using if you get a Desert Key, though not the end of the world if you do not. The only reason you should still be using Firecracker at this stage.
Ravens - Good damage and doesn't trigger invincibility frames, but suffers a similar fate to the early game Finch. Can sometimes get stuck flying in circles and reducing damage concurrently. Can be quite strong though, and works well with the Dark Harvest.
Deadly Sphere - With a name like that, and with how cool they look, you would think this staff is very strong. And it is! But! It dashes through enemies, often times hitting them once and taking forever to hit them again. Not worth the waiting and RNG required to use, IMO. Can't remember if it attacks or floats through walls even, in desperate need of a buff (though will most likely not receive one, as we are supposed to have received our last update)
XENO (UFO'S) - Very strong summon! Attacks are fairly instantaneous and are almost impossible to dodge. The go-to post golem staff that will most likely only be replaced by the stardust weapons. Incredibly strong and will make short work of most enemies.
Terraprisma - Good luck getting this one. Unless you're on Journey, you probably won't be getting this summon until after it is useful. I wouldn't know, never got it. But it looks like it will be incredibly strong. Downside is, they will ignore your whip targets, but they will defend you better than any other summon as all swords sit directly beside you and attack nearest enemy even through walls.
Stardust Cell - One of the best options, little floating orbs that teleport to where you need them and instantly start attacking your target. Will also stick enemies with stardust orbs, ticking for a big 10 damage per second, per orb (doesn't seem to be a limit, besides one stick per minion). Used in your more mobile fights like Pillar Invasions and Empress of Light.
Stardust Dragon - My personal favorite. Will attack whatever you whip, or will prioritize the furthest enemy on it's own. Can and will attack through walls, and gets more segments per minion summoned (and also more damage). Does ridiculous damage with the firecracker, and will fly in circles on stationary enemies (like moon lord if you can hold him still) dealing an absolutely stupid amount of damage.