Sounds the same to me, then again I'm not exactly the pickiest or most observant listener. But it could be. Match actually downloads the 256kbps (if memory servers) version of the track, though it starts playing before the download completes.
I don't know what iTunes Radio does for streaming, but even a high quality stream is likely to be more compressed than an actuall download. And it might adjust for bandwidth, so that quality could vary.
Edit: Checked. Yes iTunes Match uses 256 kpbs quality files, even if the ones you had on the computer were of lower quality. The only exceptions would be those lower quality files that Match could not match, and had to upload to iCloud.