I vote for the Mamiya 6 or 7. The Mamiya's are fabulous hand held cameras that have very sharp optics. I have the mamiya 6 and all 3 lenses (50, 75, 150)-- the limit of 3 lenses is the drawback-- and can whole heartedly recommend for travel.
The retractable lens mount makes the Mamiya 6 one of, if not, the most portable med formate cameras. The camera is about the size of medium sized paperback book.
Mamiya can no longer fix the achilles heel of this camera for lack of parts. That being the film advance gears can strip over time. This has also driven up the cost of the bodies on the used market. Expect to pay 600 -850 for the body (the MF's being at the higher end). A used Mamiya 7 body will go for 700-1000 (the 7II being at the high end). The lenses for the Mamiya 6 can be had for relatively cheap and if you can find someone who is selling all lenses and body together the price per component will be really cheap. http://www.Harryscamera.com had a great deal on the complete set (I believe it worked out to be about 1800.00 usd).
I know this because my winder recently bit the dust and I was forced to look for a new body and or contemplate the switch to the 7.
Hope that helps,