This post made me really curious, so I geeked out an exact comparison between Twitch and Kalista E:
Base Damage
Kalista E: 20 / 30 / 40 / 50 / 60 (+ 60% AD) << It Scales
Twitch E: 20 / 35 / 50 / 65 / 80
Extra "Stack" (Twitch Limited to 6, Kalista Limited to Number of Spears in 4 Second Window)
Kalista: 10 / 14 / 19 / 25 / 32 (+ 20 / 22.5 / 25 / 27.5 / 30% AD)
Twitch: 15 / 20 / 25 / 30 / 35 (+ 20% AP) (+ 25% bonus AD)
Twitch Only: Each Stack also does 12 / 18 / 24 / 30 / 36 (Max 72 / 108 / 144 / 180 / 216) TRUE DAMAGE over 6 Seconds, at Levels 1 / 5 / 9 / 13 / 17
Kalista Only: SLOW: 25 / 30 / 35 / 40 / 45%
Mana Cost
Kalista: 40 MANA (100% mana returned if it Kills any target)
Twitch: 50 / 60 / 70 / 80 / 90 MANA
Main Differences:
- Kalista base damage scales with AD (full AD, not bonus AD)
- Twitch has his slow on W, for 2 Stacks (same leveling of slow as Kalista E), this does 24-72 TRUE Damage over 6 seconds depending on level
- Twitch Extra Stack damage scales with Bonus AD and AP (who builds AP on Twitch?) vs Kalista which scales with Full AD
- Twitch can continue to add more Deadly Venom Stacks while E on Cooldown, Kalista can not unless she Rend-kills minion or champ
- Kalista has 2s higher cooldown initially (14 vs 12 seconds), but both end at 8 seconds at max rank
- Kalista can have instant cooldown + refunded mana
- Twitch wants Slow (W) + E, it will cost him 2x-4x the Mana of Kalista E depending on E Rank, at Rank 1 W and Rank 3 E, it costs 120 Mana, but Kalista E costs 40 Mana
Damage Comparison 4 Stacks LEVEL 1
Champ Level 1
Rank 1 - E
Doran Blade
Standard Runes and Masteries (AD Marks, AS Quints), Ignoring Warlord Mastery
4 Auto Attacks
Twitch
Base AD: 49
Bonus AD: 19
Total AD: 68
48 True Damage over 6 Seconds (plus potentially extra ticks of 12 damage for time it takes for 4 auto's)
224 Damage from AA
99 Damage from E Base and Stacks
Total: 323 Damage + 48 True Damage (over 6 seconds) (50 Mana)
Kalista
Base AD: 53
Bonus AD: 19
Total AD: 72
288 Damage from AA
63 Damage from E Base
43 Damage from E Extra Stacks
Total: 394 Damage + 25 % Slow (40 Mana)
Now Level 6....
Damage Comparison 4 Stacks LEVEL 6
Champ Level 6
Rank 3 - E
Doran Blade
Bilgewater Cutlass
Standard Runes and Masteries (AD Marks, AS Quints), Ignoring Warlord Mastery
4 Auto Attacks
Twitch
Base AD: 61
Bonus AD: 47
Total AD: 108
72 True Damage over 6 Seconds (plus potentially extra ticks of 12 damage for time it takes for 4 auto's)
432 Damage from AA
197 Damage from E Base + E Stacks
Total: 629 Damage + 72 True Damage (over 6 seconds) (70 mana)
Kalista
Base AD: 66
Bonus AD: 47
Total AD: 113
452 Damage from AA
108 Damage from E Base
141 Damage from E Extra Stacks
Total: 701 Damage + 35 % Slow (40 Mana)
Summary
If Twitch uses W and E, it costs him 2x - 4x the Mana of Kalista, and Kalista can get a Mana + Cooldown Refund if she tags a minion that will die with Rend. Damage is quite similar, if not leaning towards Twitch a little maybe cause of True Damage.... unless Kalista can get crazy number of spears in you, but at equal stacks, Twitch and Kalista damage are about even.
Of course the full Kalista kit might be a different story, her W passive being proc'd by bind-buddy can really change total damage output a lot.
EDIT: Updated the E damage on Twitch, had confused with Kalista "additional spears", Twitch damages equally for all stacks + base damage.