We've used our Reimo in some truly dreadful conditions last year, in heavy rain and wind. It was absolutely fine. It had to spend a while stowed before I had a chance to get it up and dried and can report no issues. Ours has the integrated mattress on a proper, trimmed, base, into which are neatly integrated some led lights which light the interior well of an evening. It's very comfortable indeed.
The main thing we found was that while it's ok for one, getting up in the night (as you do) makes for some interesting contortions to try and avoid your sleeping partner! Turning round so you can get down is challenging if there's someone beside you. It may be possible to sleep with your head to the rear, but I've found this too claustrophobic, even with the relatively high roof at the back. For this reason we've ended up using the seat/bed instead when we're both away.
However, if solo, we've both found it's simpler to just leave the seat (and table) as is and go sleep "upstairs". In truth, we were hoping the pop-top bed would have been our go-to sleeping arrangement, but it's proved not ideal. It will be useful for our nieces though when they come out with us.
People are commenting that the lower profile of some of the roofs on offer looks better, and I'd agree with this. However, at the end of the day it should be about having a practical set-up rather than "looks". I appreciate the visual aspect of modd'ing vans, but by way of example I can't see the point of having a super low van on big wheels when so many people then report problems with harsh ride, tyre wear and cracked alloys. The same is true for pop-tops. A super low pop-top won't have the space for a mattress (or indeed any bedding) so you'll just end up storing it in the wagon where it takes up space. And as for seeing exposed bed-boards / slats, that just strikes me as really unacceptable. Equally, there are many people who put lovely furniture etc in their vans and then never use the hob as they don't want the van to smell of cooking. Fair enough. We cook in the van, but that's what we bought it for, not as a show-piece.
I rather suspect there's little to choose between SCA (from what I hear and read) and Reimo. Both seem to be quality items and certainly Exploria did a superb install of the Reimo on ours. I suspect it's as with all things, you get what you pay for. And neither are what could be called cheap. The other key aspect I noted in a previous reply is the load rating of the roof, and now that we've had a chance to use it with it's roofrack and two big sea kayaks on, I have to say I'm impressed thus far. It's absolutely solid, even at m/way speed and I note no movement, rattles or anything else of concern - so far anyway. This was a key factor for us, and one I was concerned about initially.
I can't comment on the genuine Cali roof although the ones I've seen appear to be fine notwithstanding the corrosion problems I've noted too.