Are all "Slide Outs" created equally? What to look for

Thanks for the info and replies.

It was said the quality of the RV is what counts most.
Where can I find out what the top (Best built) RVs are? Is there a list?

How do the slider seals work. What keeps the rain from leaking in (is there a roll across awning like mechanism that covers the top seam, or some sort of rubber seal that slides along the body?

Where can I learn more about this?