^^^ this
stitched a7r raw files are really nice... there are several examples of stitched photos in the top row of this link, blow 'em up to 100%, and scroll around in the photo :
Death Valley photos, shot with a Sony a7R and legacy SLR camera lenses
one big downside to the a7r is that it's very hard on wide-angle glass, you can see that in the 24mm comparisons that i did at the above-listed website... a7 probably gets the nod for fewer problems with lens field curvature, but it has issues with sensor reflection, in extreme light situations... pinholecam has posted some examples of that out here... with normal use, it won't be a problem at all.
if you need to use flashes, the sony platform can be really weak... they changed flash mounts, which is a huge hassle... and while the flagship f60m flash is a real flamethrower, it has a bad rep for overheating... hss doesn't work when the f60m head is pointed up, and the head won't rotate from side to side
radio transmitters for the sony flash platform are few and far between, and the best option for that, phottix odin, apparently has issues that have just come to light.