For small and modern, its either a Mamiya 6 (late model not the folder) or a Mamiya 7. I have never owned either but they both get good reviews.
So far I have owned a Mamiya press, Mamiya RZ, Mamiya RB pro-s, Fuji 617, Fuji B690GL, Kowa super 66, a couple of old folders, and I now own a Pentax 67.
The links are to 2000 dpi drum scans. I think the 617 is 1500 dpi.
The press is too heavy, but very manual and very versatile. The 50mm lens is sharp too. You can shoot anything from 645 to 6x9 with interchangeable backs.
Here is a 6x9 Press picture with 50mm lens handheld.
http://www.pbase.com/tammons/image/26475621/large
The Mamiya RZ is very nice, good sharpness, very smooth mirror, I mean very smooth, great rotating back, interchangeable backs etc. Very nice.
The RB67 pro-s is the manual version of the RZ and I actually preferred it, no batteries, everything as above and they did make a 6x8 back for it.
Also both the RZ and RZ have a tilt shift adapter you could hook up to the front, but they really belong on a tripod 100% of the time. Difficult to hand hold, but I have gotten some good 1/60th handheld shots with it. Both have a great viewfinder.
Here is an RZ shot with a 110mm lens.....
Please excuse the scan lines. My scanner was acting up that day.
Check out the lizard in the upper left.
http://www.pbase.com/tammons/image/40591721/large
The Fuji 617 is a beast, no focus assist, terrible framing and basically just a LF lens hooked to a film back. Heavy and huge, tripod only, but the photos are spectacular. I really expected it to be a bit sharper. I have a sironar 150mm 4x5 lens that I think is sharper than the 105 Fuji lens. A camera that is perfect for wide open spaces.
Here is a 617 photo.......
http://www.pbase.com/tammons/image/40591847/large
The Fuji B690BL is another heavy camera, range finder with interchangeable lenses. Its like a giant Leica. Actually they nicknamed them Texas Leicas. I had a 65mm lens and a 100mm lens. The 65 was sharp. It was very hand holdable, but heavy. The viewfinder was terrible, but the pictures were nice. My 100mm lens was average.
Here is a B690GL photo.......
http://www.pbase.com/tammons/image/40594191/large
The Kowa super 66 was the bargain camera of the year for me when I bought it. Cheap and sharp. Good if it has not been abused. Abuse them and they tend to lock up. Lenses other than the 85mm are hard to find.
Here is a Kowa super 66 photo......
http://upload.pbase.com/tammons/image/37003452/large
As far as the old folders forget most of them and go for modern lenses. Fuji and Plaubel made a couple of modern folders.
The Pentax 67 is probably the most versatile with a huge selection of decent lenses, but its a tank too. Its like a giant 35mm SLR camera. The thing I really don't like about it is the violent mirror slap. If it had the soft slap of the RB and a rotating removable back it would be perfect, but still I am sticking with it. For hiking or low light handheld a Mamiya 6 or 7 would be a better choice, but the lens cost for the 7 are nuts.
Here is a Pentax 67 photo.....
http://www.pbase.com/tammons/image/40467679/large
Its really a tough call and the one camera I really want to shoot for a while is a Hassy, but i am afraid that if I pick one up, I will like it so much I will have to buy some very expensive lenses to go with it.