I don't have the exact model, but my iGPU is the same as yours. I have a maxed out late 2013 15" rMBP. It runs totally fine for me (I didn't bother with a clean install). I would say the same speed (or a little faster) as Mavericks, but I've been running Yosemite since PB1 so it's been a while since I was on Mavericks.
The consensus seems to be that Yosemite runs just as well as Mavericks. Many people are running way worse specs then you have. I wouldn't worry about it at all.