The remora is very sensitive to oils in the water and salinity, but performs well for price generally.
The corallife is more consistent (being a needlewheel) but is big and fugly.
"The best" HOB skimmers (I'm assuming you have no sump) that I've seen are the Tunze 9010 (more than the remora and the corallife but you'll get an upgrade in performance and it's very petite) and the Deltec MCE600 (much more expensive but better performance though probably not so much better that you'll come to accept the price difference and be at peace with how much you paid for it : )
I was looking at both of those skimmers a few months ago and all of my research was pointing to the Remora. I have heard a lot of good things about it. I ended up doing an entirely new aquarium w/overflow and sump, so I bought a Euroreef--its awesome!!
I do not have any experience w/ the "seaclone", but I have heard that it is not very good. Save your $ and buy a nice skimmer that you know will do what you want it to. My Euroreef was about twice what I wanted to spend on a skimmer, but I couldn't be happier with it.