Originally posted by ElJamoquio a) FF was cheaper for me (equivalent photo capability, more or less)
b) a wash for me
c) FF was lighter for me (equivalent photo capability, more or less)
d) Sometimes/usually... but the highest FPS I'm aware for a mirror up/down system is the D4S
e) larger files goes with higher MP. The lowest-end FF and the highest-end APS-C's (where comparison between the two makes the most sense to me) both have 24 MP files
f) same as e)
If you're OK with F/4 or so on APS-C there's really not a lot to gain on FF other than the viewfinder, IMO. I wanted F/2.8 (or faster) on APS-C which drove me to FF.
You also didn't mention that FF is more tolerant of cropping than APS-C. Basically you get a FF and an APS-C lens all in one.
I think cost is a really tough thing. It isn't that expensive to get a K50 with a 18-55/55-300/DA 35 f2.4/DA 50 f1.8 combo. You would be able to get that combo for under a thousand new and obviously getting used gear you could save even more. If you are insistent on getting expensive gear, it is available for full frame too.
I really come down to the fact that there isn't that much difference in formats unless you are shooting at the extremes. If you are in the middle with regard to isos, apertures -- an average shooter -- it is unlikely to give you some kind of dramatic difference. In addition, people try to put numbers on these things -- 20 percent sharper images, or whatever. The question is what that number means and whether it is visible in real life shooting and presentation. The answer is probably not for the majority of images out there. For a small number, APS-C may actually hold a small advantage and for a slightly larger (but still small) number full frame will hold an advantage.
I'm not sure about the whole cropping thing. Can you really crop a D600 image more than you can a K3 and get a significantly larger print size? Seems like if you have a 24 megapixel image that is pixel sharp, whatever format it is shot on, you should be able to crop it the same before you notice pixelation.
I am in the same camp as the Voice of Reason, in that I am quite used to APS-C format and would actually have to adjust to how different lenses work on full frame (and not the reverse). The Sigma 18-35 does seem to even the playing field between the formats as well, if you shoot in low light a lot.