Here’s the best summary of the brands and subrands.
@Jim_Johnstone my understanding is that Parolin parts are interchangeable, and I haven’t ran into any exceptions with my daughter’s Nitro kart. That being said, I do like dealing with the Nitro guys. They are local to me and have helped a ton in a couple pinches. I just texted one the other evening to have some parts on Friday because my daughter broke an exhaust bracket last Saturday.
Same for my Maranello which is a rebranded CRG. The Prodigy team is also local and dealt with Maranello, so I try to go through them when I can. They’re phasing over to BestKart now (or maybe both, I can’t speak for them), but they still have spares I can pick through.
Any time anyone asks “which chassis should I go with” the answer on here is invariably “go with what has local support”. I’ll buy generic parts online pretty often, but there’s a huge advantage to being able to run across the paddock and grab a part. If the local team you like to work with supports Parolin, I’d run Parolin. If they’re Nitro, I’d run Nitro. Just don’t put yourself in a position where you can’t replace a part on race day because no one has it on hand.