I've been on the XR version of Seroquel and on Seroquel (immediate release).

The XR version helped me stay asleep rather than the "knock out" effect that immediate release Seroquel had when I first started taking it. However, Seroquel XR made me pretty woozy throughout the day. I even felt drunk when I first started it. It is something that faded with time, but I still felt more fatigued during the day than with IR Seroquel.

I think there's pros and cons to each version. Currently, I'm on immediate release, which is a much better fit for me. Personally, I don't ever want to go back to XR. The immediate release still makes me a little dizzy on certain mornings where I don't take it early enough, but that feeling doesn't last. I also like how it is more powerful when it comes to getting to sleep compared to the XR for me.

I don't think it's a matter of better or worse. There's just some differences.