Are you going for a Rollei SLX or sticking with the Mamiya?
Heres my thoughts on the Rollei's
I have looked, on and off, over the years at the Rollei systems and almost buying a 6008i.
They are all electronic and most, including the SLX, have a built in meter, I think the SLX is centre weighted, the 6008 range offers a couple of other metering options.
Loading the film in these things is probably on of the easiest to with the way that Rollei has designed their film cartridges.
The BIG down side to the Rollei systems is its power unit,
They are all electronic and no power nothing works, no back up mechanical settings ala Nikon F3.
The batteries are Nicads and you can find replacements or refurbed ones on Flea Bay but they are not common, I think there were a couple of webites around that showed you how you could replace the batteries and I think you would have to be handy with a soldering iron.
Other than that they are cracking cameras, lens, cost wise are about on par with Hasselblad.
Oh and the Rollei 6008AF was I think the only film Rollei that did auto focus, excluding the Digital one they did, which the model name escapes me for the moment.
Other than that.
Stick with the Mamiya, and the tweed