I doubt it would effect games very much, it's possible but it would depend on the specific game.
With video editing you will mostly notice a bump in speed when doing things like importing and exporting video or applying filters/effects, since those are pretty CPU intensive.
With Photoshop you might notice when applying filters to large images.
Mostly just a few seconds here and there when you get to something that actually loads down the CPU.
Are you looking at the Retina MBP or the non-retina? Since there are some other things bundled with the 2.6Ghz models of each.
On the non-retina you get 1GB video memory with the 2.6Ghz model, which can help with games. On the Retina model the 2.6Ghz comes with the 512GB SSD, which could come in handy if you're working with large video and Photoshop files.