Would somebody be good enough to provide a picture comparing the size of Fed 1 and 2, maybe alongside something like a Biro for size reference?
I'm trying to decide between the two with the Industar 22 collapsible lens. The longer rangefinder base on the Fed 2 is appealing but size is important.
The FED-2 should be your choice if you are looking for a user camera. Aside from quicker loading (back slides off in a FED-2; FED-1 is a bottom loader), the combined VF/RF, flash synch, strap lugs (depending on production), and the aforementioned base length make the FED-2 the better choice. Size and weight are only slightly more, compared to the FED-1.
Note too that the collapsible Industar-22 and Industar -50 cannot be easily used, if not impossible, on the FED-2. The lens mount flange is sunk well into the level of the camera vulcanite. The locking focus tabs of the I-22/I-50 will catch on the vulcanite and damage it. Or else you may not be able to focus all the way to infinity. A modified version of the I-10 ("FED-50") was made for the FED-2. Instead of the spring loaded locking tab, this I-10 has a clip instead.