With a difference of ~$100 between the two, I'd go for the i7 (prices on individual processors from
www.newegg.com).
The processor is one of the more difficult pieces to individually upgrade as, depending on where you start, you're going to be limited by your motherboard. Whereas both RAM and Video Cards are relatively easy to upgrade by themselves. Going for the larger processor will also allow the system to last longer, as you're at a higher level of technology. This is especially important if you're looking at laptops over desktops, as those are nearly impossible to upgrade with the exception of RAM and Hard Drives (with a few exceptions, but you pay for that ability!)
The export process for both photo and video does put a lot of strain on the processor. I know that mine hovers between about 75%-100% while exporting a batch from Lightroom. (Intel i7 Quad Core 2.66GHz, and some other stuff). This is not a place you want to skimp on if you're going to be doing a lot of that stuff.
However, with all that said, if you're not going to be using it for serious video editing, and the extra money could potentially be an issue, it appears that the i5 WILL work just fine. It just may take a little extra time to render/export. There are also likely other factors at play, including hard drive and bus speed that is still (after 11+ years of working in the computer industry) is a bit above my head.... (I'm more of a software guy than a hardware guy... yeah, that's it)
ETA: As a note, I'm also sitting on 12GB of triple-channel ram (uses 3 sticks at a time, instead of the normal 2) and a 1GB ATI HD5770 Video card (used to be dual video cards, but one blew out)... I also AM a gamer
