I've done three trigger spring kits from M*CARBO. 75B, P-01, and 97B. Great way to understand how the internals work together. Good results. I did do some machine marks removal and general polishing on certain moving parts I'm sure contributed to the results.
Even if later you decide to go with a self-installed CGW kit, the experience you gain rather inexpensively from M*CARBO is well worth it.
So far, I've not found the need to go with a CGW kit as I'm satisfied with what I got with the M*CARBO. Trigger pull reductions in DA/SA between 35-45%. Polishing made a difference too.