One of the cool things about camera comparisons is Google! (not trying to be a smartass, btw) I was trying to decide between saving up for the D7000 or D7100 as my next body upgrade, and was looking for comparisons in Google and ran across the site I will link below. I put up a link for your specific question, but it will compare any of the Nikon models to each other (as well as other brands) and weigh out basic pros and cons for ya. It's not an end all comparison, as there are some questions that only those who have used both can answer (like above), but it's a nice comparison of the tech specs.
PLUS, I wouldn't always trust the top score as to who it says is the winner, and I'll put this out as an example. I just tested to see if it would compare competing brands, and comparing the Nikon D3100 to the Canon t3i, it declares the Canon the winner, but, under the advantages of the Nikon it lists: Lower noise at higher ISO, Video autofocus (t3i has none), Less startup delay, Better color depth, Better image quality, Longer battery life, More focus points... and Cheaper! *shrug* Still gives ya a great comparison.
If ya DO upgrade, I'd recommend as soon as possible so you can be very comfortable with the new camera well before the wedding, as those are shots you don't want to mess up.
Nikon D610 vs D7100 - Our Analysis
Having said all that, I'm jealous of both cameras! I'd do backflips for a D610, but don't see that happening anywhere in the near or semi-near future. I'd also be pretty durn excited over the D7100, and it's my goal to have one of those by the end of the year (might take me 2).