It wasn't mentioned where the travel is to, what subject matter is of interest and how the equipment is to be carried. Personally, I use Hasselblads and take the 50FLE, 150 and a 2x and carry all plus a Gortex shell in a camera backpack. I pack a daypack in my checked luggage and use that if in a city to keep weight and size down. I like to have each of the lenses on a separate body using the same film in both so there is no need for switching lenses. The 2x is for out in the countryside. I have an 80, 250 and 350 and extension tubes but would only take one or more of them if I knew I would really have the need. The other stuff is heavy enough as it is.
I've got my 500cm and C220 in front of me now, both fitted with an 80mm lenses (the 'blad with a chrome T*). With the 500cm sitting on it's base and the C220 lying on it's back, side by side, the Mamiya is approx 2cm wider than the 'blad (due to the focus wheels) and about 1cm higher - the lens sticks out more than the wlf. The Mamiya is 100gm heavier than the 'blad, too. So, whoever said the Mamiya was smaller was wrong. However, the difference isn't huge.
I have a chrome 50mm Distagon, too, which weighs very nearly 1kg but I don't have a Mamiya 50mm to compare it with. From memory, I'd guess that the Mamiya 50mm is slightly larger and quite possibly heavier.
Given the choice of camera, I'd say it depends what you want to do with it and price - the size/weight differences aren't vast. Personally, I tend to use the Mamiya for personal B&W stuff that doesn't need to be quite as precise as commercial work, which is usually shot on transparency. The 'blad allows me to run two backs at once as well as use polaroid (again, an absolute must for commercial applications).
Of course, as soon as I add an extra back or a polaroid back to my kit the 'blad starts to be a bulkier, heavier, option. It does have other advantages, though, such as the excellent dof scale and the useful ability to lock exposure values in step, enabling me to riff through various exposure combinations more quickly.
Prior to weighing the Mamiya, I'd have guessed it was lighter but it doesn't make me like it any less. It's less temperamental than the Hasselblad because the mechanism is simpler, I've never needed to fix anything on the Mamiya. The Hasselblad, on the other hand needs regular servicing, otherwise things tend to go wrong ; only last week I had a back jam. Luckily I had the Mamiya with me just in case...
I took a mamiya RZ67 out to the garden this morning, with metered prism and the winder... What a beast. Tripod was a necessity. Some shoot handheld buy I find it too much for me!
Then grabbed a Hasselblad 503CW with winder and metered prism. Easily handheld. What a compact system. With the manual winder and waist level, it is lighter still! Will be taking it to a wedding(I'm the best man, not the pro) for some shots end of the month and know it packs well, works well and will be perfect.
Have you decided on anything yet?