I know wired is typically faster and more reliable, but with my specific case of a 25mbit isp, a dual band wireless N router, and about a 15ft length betweeen the PC and router, would the wireless adapter be able to net a constant 25mbit as well?
As Emerald said, wired still is best but being that you are so close to your router, and likely the ISP speed being your bottleneck, you probably won't notice much difference. For the $20 bucks or so its worth it to get rid of that wire!
WiFi is a shared medium (half-duplex with potential collisions etc.) so if you are the only one wirelessly connecting, your connection will be awesome. If you have 5 other people connecting, then you'll really feel more of a performance hit (more so than if they were wired).