Remy: Fusions are special. AFAIU the Fusion is a love-or-hate object, with very little middle ground. I looked at a Fusion when my son was shopping for a new DS. Neither he nor I liked the construction; it seemed like a serious hassle to don and doff compared to a normal back- or frontzip suit with normal undergarments.
My first DS was a compressed neoprene suit (ScubaPro Everdry 4). It's very easy to dive, snug and stretchy like a WS with a tiny air bubble and virtually no air travel. Light legs or boots popping off is a non-issue. From what I saw of the Fusion we considered, I'd assume that it shared some of those properties and that that is what makes people like it. My problem with the Scubapro was that it didn't provide room for thick winter undergarments, so keeping warm during winter diving was a bit difficult. I only had room for a couple of layers of not-too-thick wool underwear, but I guess if I'd gotten it a size or two larger that would've been different. OTOH, air travel would have been more of an issue. My second DS is a trilam suit, a WaterProof D7. It has room for really thick undergarments, and properly weighted for winter temps (i.e. slightly overweighted according to SB consensus), I have plenty of loft and air inside the suit to keep me warm even in near-freezing water temps. The downside is of course that the bubble is bigger, I need to be more aware of air travel, and the larger amounts of air vent slower through my undergarment than the thin layer of air inside the ScubaPro does. Another disadvantage of the trilam suit is that the fabric isn't stretchy, so I feel noticeably more constriction from that suit than from the ScubaPro. Win some, lose some. TANSTAAFL.
Since I haven't been able to find a buyer for the neoprene suit, I'm using it when the water temp rises above ~10C (which it seldom does around here, but it happens more often a little bit further South), but for >75% of my dives, I'm using the trilam. I'd like to use the neoprene suit more, because it's almost as easy to dive as a wetsuit.
I've also heard the "get a trilam" mantra, but I have several clubmates who seem very happy with their (compressed or crushed) neoprene suits and don't se any reason to switch to trilam. I guess preferred type of DS is a combination of personal preference, prioritizing different properties and, of course, a bit of post-purchase rationalization