On second thought, you should buy the ro. I want to get that bm. Haha.... I think I know where you see both for sale.
Opening caveat: I've never owned either.
With that, I'd first look at the amount of space you'll have in your sump. If either will fit, look at the optimal water height. If they're the same, look at which one uses the least amount of power. I'd be willing to bet dollars to cents that actual performance, post-break-in, between these two will be indistinguishable. I've heard Coralvue's warranty and customer service were pretty good, however, I haven't had to use either for the Coralvue products I own.
I personally consider noise as a huge factor, but these smaller pump skimmers don't usually create too much noise.
What size tank?
its a 48" 90g , im making a new sump so I can accommodate the sump around the skimmer
Not claiming to be an expert, but I think you'll get more contact time with the external pump so, if you're making a new sump anyway, I'd go with the RO.
And, if I can make another recommendation, design the sump so your drain line feeds into the same chamber as your skimmer --> over-under-over weir --> return chamber ---> single baffle --> refugium. Feed the refugium from your main drain via a t-fitting + small gate valve or a little maxi-mini pump from the same chamber your return pump is in. That configuration will minimize the amount of microbubbles you'll have to deal with.
Just a suggestion based on my experience with not doing it that way. I have my return pump in the same chamber as my skimmer and had to make some modifications to minimize the bubbles even after break-in.
I was going to do water splashing over lr baffle then skimmer section then fuge then bubble trap to return