Being that I have been in gunfights and that I am currently competing in my area at the top 3 level of my divisions of IDPA, I would say that competition is a great tool and allows for building proficiency at a more skilled level. However, I would not compare competition as the same as my past combat experiences. I would also say that USPSA/IPSC race gunning equipment is not a good tool to use for preparing for combat (i.e. a gun fight).
A Serpa holster requires more movement then a quick draw race holster, it requires more muscle memory and it requires more concentration. The same way that a Level 1,2,3 security holster is slower, and requires all of the above to use. The same way that compensators give less recoil, optics allow for quicker sight alignment and sight picture. As well as the way that extended magazine capacity allows for less reloads and light trigger allow for more relaxed trigger control.
When shooting race gun equipment I have easily been able to shave time off of my stage runs, with better accuracy. That in its self shows me that it’s not practical to practice with equipment that I won’t use in combat, b/c it gives me false results.
All in all, I will always recommend people shoot in competition to further expand on their proficiency and skill levels. However, I would tell them to do it with the weapon, equipment and clothing that they would be using when faced with using that equipment in real life (i.e. full PPE for soldiers, duty belt for LEO’s and the way you dress and carry when out on the town).