Is it possible that you could hire/borrow/rent each kit for a few days to play with? This is one of those cases where you can get answers to the questions you're asking (which are important), but you won't get the answers to the questions you don't know to ask. Hands on shooting in your actual desired scenarios is the only way to get a thorough idea of which camera takes on the magical attribute of becoming an extension of your artistic will, and produces the quality you're after.
Notably with an H1+P45 if either
the back or the body has problems you could rent another in a heartbeat in any major photo city (NYC/Miami/LA for sure, and most other big cities).
Other people's opinion on ISO200 is not going to get you very far. You need to get sample raw files (or better yet capture your own) to evaluate. Notably Capture One v7 does MUCH better at high ISO on Phase One digital backs
. So anyone who last looked at an ISO200/P45 file in Capture One v6 would be giving you an outdated opinion on it's quality. The amount of fine tuning that is done in Denmark by the C1 team for P1 backs is truly remarkable; the hardware guys are literally down the hall and share drinks and financial motivation to make them sing well together.
The P45 is not traditionally my suggestion for environmental portraiture. It's frame rate is one of the slowest in the P1 lineup (0.7 fps). For your application I might normally suggest a P30+, P40+ or a P65+. That said, if you don't shoot very quickly and you favor frame size, and resolution over speed and high ISO performance than a P45 might be a good fit.
Which brings me to my trope... it's really better to start your search wide, and determine what the best tool for the job is and THEN find a good deal on it, rather than first find good deals and evaluate if they are a good tool for the job.