I don't think TWF gives rogues a better chance to crit on sneak attack, since no one's going to hit their first attack then decide to chance a second attack to see if they can crit. If your DM has you roll all your turn's attacks at once, then that is one boon.
The big consideration you overlooked is that attacking with advantage with a rapier (or light crossbow) is better than attacking twice using TWF. Attacking twice with a Hand Crossbow is slightly better than that. Assassins prefer the extra attacks for surprise rounds, but Arcane Tricksters and Thieves may be better off hiding or otherwise distracting for Advantage.
[sblock]Level 20, two short swords.
8.5*.65+3.5*.65+35*.8775+42*.05=40.6125.
Level 20, rapier, advantage
44.5*.8775+39.5*.0975=42.9
Level 1, two short swords.
6.5*.65+3.5*.65+3.5*.8775+10.5*.05=10.09625
Level 1, Rapier, advantage.
11*.8775+8*.0975=10.4325[/sblock]
The big consideration you overlooked is that attacking with advantage with a rapier (or light crossbow) is better than attacking twice using TWF. Attacking twice with a Hand Crossbow is slightly better than that. Assassins prefer the extra attacks for surprise rounds, but Arcane Tricksters and Thieves may be better off hiding or otherwise distracting for Advantage.
[sblock]Level 20, two short swords.
8.5*.65+3.5*.65+35*.8775+42*.05=40.6125.
Level 20, rapier, advantage
44.5*.8775+39.5*.0975=42.9
Level 1, two short swords.
6.5*.65+3.5*.65+3.5*.8775+10.5*.05=10.09625
Level 1, Rapier, advantage.
11*.8775+8*.0975=10.4325[/sblock]