Bronica ETRSi or Mamiya are good choices. As for which is better, well either are on the same playing field in quality. I prefered the ETRSi because of price n availability... Also lenses are cheaper n plentyful as well as a wide assortment of accessories.
As for 6x7... Hahaha you won't realize the difference till you own one! 645 will give you very pleasing prints n you'll be amazed everytime you print.
BUT.... that very first time you print a 6x7... You will be blown away!... I mean right out of the water!
But then the very first time you print a 4x5... Holy crap!
See the rollercoaster ride in your future? Where does it end?... It ends when the wife cuts up your charge cards!!!
Ask me how i know?
Btw, get that meter and don't spare on expense! It is your main crutch n will make your life that much easier.