Put me in the crop camp. I would never want to walk into a wedding without the versatility of a crop body. Your options are far greater with both formats. Especially for receptions, I basically throw the FF cam in the bag and shoot exclusively with my 40d. 200mm on crop lets you stand MUCH further back and be more invisible. Actually, i shoot most of the day primarily on crop. I have found the image quality if the 40d to be superb, great enough that I have no image quality concerns whatsoever. I shoot right up to the iso 3200 ceiling without hesitation. Are newer FF bodies delivering better image quality? Well, yes, but to me it is just not actually offering anything extra that makes a practical difference. I don't get any less shots without FF, i don't make any extra print sales because of FF, and in fact, I can get shots from further away with my cropper than I wouldn't get with my FF setup. Its just more flexibility in your arsenal.
To br perfectly honest, if i HAD to choose between having two FF bodies or two crops, I would take the two crops. I just think FF is so overhyped and unnecessary. The only thing it gives you is 1.3 stops of less DOF, but if you actually want to get a photo with more than one person actually in focus, you want a little more dof, not less.
Not to mention, having shot weddings with a 40d and 5Dmk1 combo, the 40d autofocus performance stomps all over the 5D.