The 360 Beta had a lot of log-in issues, which, in my opinion, was due to server stress from the sheer amount of players trying to play at once. they did a patch, which kinda alleviated the problem, but not completely wiped it out. for me, the beta has been working great, after the first day. very smooth.
Also, the 360 and PS3 Betas was running a 2 1/2 Month old build. the PC Beta Version is the most recent build, and it shows. the graphics, particularly, are much better in the PC Build than the old build we got. This information came from the following post by the Trion World Community Manager on the Official Defiance forums: