In my view it is more important to contemplate the aspect ratio first, and perhaps the shooting style second, before jumping into a MF system.
One of the attractions of MF is the fact that different aspect ratios exist, and these can be very appealing in their own way. Hasselblad and most TLR's produce square 6x6 format. It takes some getting used to, to appreciate and compose in square format. It does have its own magic, no doubt about it. The 645 and 6x8 systems are 4:3, and the 6x7 is very close to 8x10 paper. If you are going to do darkroom printing, your format will determine how much cropping in which direction you'll have to do to fit in on a standard paper size. Alternatively you will be doing a bit of paper trimming on a guillotine. All MF aspect ratios apart from square work better on standard paper sizes than does 35 mm with its 3:2 (which is only good for jumbo i.e. 4"x6" prints). For me 645 is the sweet spot, as I print a lot on 12" x 16", and it crops minimally down to 8" x 10". I also have two 6x7 systems, especially if I want more detail after scanning. Of course one can make a mighty fine print from those as well. 6x7 prints onto 11" x 14" or 8" x 10" with virtually no cropping. At those sizes, grain will be just about invisible for normal speed films. Since 645 is good enough for my largest print sizes by a comfortable margin, the fact that it stretches the film further (15-16 vs 10 exp) allows for more experimental shooting and fewer roll changes.
As for shooting style: Shooting at eye level with a prism finder vs shooting with a waist level finder are two quite different approaches. It is for this reason that I still keep my RZ Pro system, as it is great for waist level and lower angle shots. The TLRs are also mostly used in this way, but they do not come close to the close-focusing abilities of the RZ Pro. Most serious cameras come with both WLF and prism finder options and possibly others such as turrets, but there is usually a particular type of finder that feels more "right" for a given camera than the other types. For the Hasselblad and Mamiya RB/RZ type cameras, that is arguably the waist level finder. For the Pentax 6x7 it is arguably the prism finder. For this reason more than others, my RZ and Pentax 67 images look different, because they were mostly taken from different perspectives. WLFs don't offer metering, so if TTL metering and auto exposure are important to you, then a metering prism finder is what you have to get.
There are lots to like and dislike between different brands, but the above are in my view more important primary considerations. I have Mamiya systems in 6x7 (RZ) and 645 (Pro TL and AF-D II), as well as Pentax 67 II plus a fairly comprehensive set of lenses. They are all excellent, and I never have a worry about the quality of the results I can achieve. It is more about what output I want, which lenses I want to use etc. I happen to have the 80/1.9 Mamiya lens, which I bought with the Pro TL. That is a very nice combination, to say the least. You would not think as much of 645 if you used lesser lenses on it, but even then it is loads easier and more fun than printing from 35 mm. I am not saying 35 mm lenses aren't sharp enough, but you really need to know your craft to get consistent good large prints from 35 mm negatives. As for Bronica, Hasselblad, Contax, Fuji etc I have heard only good things about them. The MF systems are almost all excellent, though some are more expensive to maintain or more difficult to find parts and accessories for.