Here are my personal opinions:
I had 85Combat and SP-01 at the same time and ended up selling Combat - it felt way to muzzle light to me. Balance of Combat felt wrong. Accuracy suffered with it where I shot much better with SP-01.
Then I discovered Shadow, still have both
![Smiley :)](https://czfirearms.us/Smileys/default/smiley.gif)
Personally, I think it makes no sense to competitevely shoot Limited Minor. Either go with 75SA in .40 and shoot Limited and IDPA ESP with it or 1911 or Tactical Sport in .40 to shoot Limited.
If you are new to the sport, have limited budget or don't know which way to go and whether you'll be shooting competively 2 years later - shoot what you have and work on improving.
If I were to start over again with what little I know now and little experience I got - I'd go with Shadow for IPSC/USPSA Prod from scratch.
Most likely would use either Tactical Sport or STI Edge in .40 for Limited and STI Spartan for IDPA CDP/ Single Stack.
With your Stainless gun - it can def use better than factory sights, and shiny guns tend to distract/blind shooter while running, turning, shooting and reloading outside on a sunny day.
Grip wise - both 75B and SP-01 have same angle, you won't need to re-learn or adjust there.
It's hard to even attempt to advise you on what to do. You need to decide yourself.