I've tried both.

I don't like regular Seroquel. I sleep waaay too much on it. Like, we're talking 12-14 hours. Not acceptable for me.

Seroquel XR lets me get 10 hours of sleep a night without having that nasty hangover the next day. So... they both have the same effects. But if you have really bad insomnia, then I don't know if Seroquel XR is going to help with that. You might want to consider regular Seroquel.