While I have never used Mamiya TLRs, - results I have seen from those cameras are awsome - sharp with great bokeh, - very very nice. However, the size of them turns me away from Mamiya TLRs and toward smaller ones. I think Autocord (Minolta) is a great camera. Well built, amazing lenses, very comfortable and intuitive bottom focusing lever. I prefer it to knob focus of nearly all other TLRs.
Built - I dont think that Rolleis are any better built than other well known brands. If you have taken a few different TLRs apart and put them together, CLA them - you would see that many are pretty much the same. Actually some are better than Rollei IMO - same materials, yet simpler to work on. Some fine TLRs like Yashicas, Kalloflex, AIRESFlex are very well built.
Lenses - well, if you are Ok with a Tessar type lens - I'd rather go with Japanese TLRs like Yashica, Minolta, etc.
However if you need a Planar - well - Rolleis are hard to beat. There were a few other TLRs with 2.8 Taking lens and "possibly" Planar, or rather "not a Tessar" formula lens, but those are hard to find and from what I hear are not vey reliable.
So, Rollei is the safest yet usually more expensive choice. Is it the best? Only you can answer that. For me - well, I have 4 TLRs - that should tell you that none of the is the best for me. Each has something I like and each draws differently, so that gives me a reason to keep all of them.
Airsflex is not pictured - it's still undergoing CLA.