For gaming, you'll see about 20-25% better performance, but it depends on your graphics card as well. But seeing as you only play games about 15% to 20% of the time, then it doesn't look like it's of the utmost importance. The FX-8350 will handle most of your games just fine and I've finished a lot of games with it (more than 10) since I got it about 20 months ago. I think it deserves more credit than it's getting in terms of gaming performance. For office apps, yeah, maybe 20% better performance too, but it also depends on your storage. For video editing, the FX-8350 will give you better performance than an i5 in highly threaded video editing apps and is, IMHO, a sound choice because you can not only save a bit of money on the CPU (the 8350 is a little cheaper than say, a Core i5 4670K), you'll also save money by not buying a new motherboard. Personally I'd opt to get an FX if I was in your shoes.
If people stick with you just because you have a Rolex on your wrist, you can bet losing them is as OK as losing an Invicta. And if they stick with you even if you only have an Invicta, losing them is as OK as losing a Rolex.