I was pretty adamant about putting a skimmer in my sump (MegaFlow 3), but eventually changed my mind and have an AquaC Remora Pro HOT on the way.
While keeping as many gadgets out of the DT as possible was my goal, I too was faced with space issues. The footprint of some skimmers was making selection problematic, as was height because even though I have the AGA stand that came with the tank, still would have been a tight squeeze. I've found there are varying "Additional height" requirements to access the skimming cup amongst the many brands and types of skimmers, and I wanted to make the skimmer as easy as possible to maintain.
Another factor is that while skimmers will still do an admiral job in the sump, they'll do their best work if they can get to the water before it's filtered (the MegaFlow dictates that the skimmer would be downstream of the filtration). Wanting to get the most skimming bang for the buck, in lieu of building/adding an additional sump solely for the skimmer or severly modifying the one I had, I started leaning toward a HOT.
After thorough investigation, I did find that the Remora is highly regarded, only marginally intrusive asthetically, and is fairly quiet.
Speaking of AquaC, their EV series of in-sump skimmers have a fairly small footprint.