I have tried several different aftermarket triggers as well as modifying my own. There are two aspects of trigger performance: pull weight and feel. I'll address these for each trigger I know. Note that if you plan to use the rifle in CMP Rimfire Sporter competition the pull weight must be at least 3 lbs.
Ruger BX: weight around 3lbs, feel is often described as creepy and soft but it's actually more like the European-style "rolling break" in which you press through the break which feels very smooth.
Ruger BX with Brimstone work: Pull weight under 2 lbs, so smooth you can hardly feel the break. I like the rolling break as it contributes to smooth trigger press.
Volquartsen: weight around 2lbs, also quite creepy and soft.
Brimstone Tier 3 (basic): weight as low as 2lbs. Excellent, crisp feel with reduced slack in the take-up.
Brimstone Tier 2 (intermediate): weight as low as 2 lbs. Even smoother and crisper, with reduced overtravel. Includes an aluminum, flat-face trigger which dramatically improves feel and control, reduces overtravel, and has a great reset using a modified trigger return system. This is my favorite modified trigger and if you have a base OEM trigger to supply for the work, is the most cost effective.
Tandemkross: Almost identical to Brimstone Tier 2, but more expensive since you're buying parts instead of just service.
Kidd Trigger Job Kit: There is no better 10/22 trigger than Kidd. Their proprietary design of the hammer/sear interface is far better than any of their competitors. You will feel almost no motion in the trigger press and reset is so short and positive it will make you laugh. This hammer/sear kit does not modify the overtravel/return system.
Kidd Single-Stage Trigger: Yes, this is expensive but totally worth it. If I were budget-constrained I'd get the Brimstone Tier 2. If cost doesn't matter, there is no trigger as good as the Kidd. No perceptible take-up, just increase the pressure of your finger and it goes bang. Overtravel is negligible and reset smooth and positive with their proprietary return plunger system. Pull weight is adjustable and I have seen some owners get it to nearly 1lb.
Kidd Two-Stage Trigger: Only relevant for bench-rest shooting. Pull weight can be under 1 lb.