For what its worth, the Fusion 8 has the advantage of having better vertical dispersion (The MMTMM design of the 4 will create a suckout off axis which on one hand controls reflection from the ceiling but on the other hand can create an uneven response if you are in fact sitting off axis) and better pattern control down to a lower frequency. I've not seen polar response graphs of the 8 so I can't say its a CD design, but the lower crossover point and overall design would allow it to at least have a chance of having CD characteristics down to a much lower frequency, which has been shown to be correlated with perceived better sound by both Harman and Geddes. Based on the design alone, if I was picking based on convenience to mount on either side of a tv, I'd pick the 4. If I was looking for the best sound in a small package, I'd pick the 8.
We would need to see measurements, especially in situ, to really get a sense of this, but there have been some case studies of MTM and MMTMM (especially the MMTMM) designs having undesirable lobing at actual listening positions in the room. It isn't that an MMTMM is a bad design, it has its purpose, it's just that the interaction of the drivers off-axis isn't as straightforward as with a 2 way design and as such people can end up with an undesirable response because they didn't realize how different their vertical response pattern is.
Not that this helps you in the slightest, but when you say loft, if the loft is an open area and the desire is to "shower" the loft area and the open area with sound that is even in tonality and constant in SPL, a CBT design is possibly better. That kind of environment mimics a space more akin to what you see in commercial installations where you really need to pay attention to the dispersion pattern. If you are only listening and only care about the sound quality within a normal listening distance of the speaker (say no more than 2.5x the width between the two speakers) then this doesn't matter, but if the desire is to fill a larger space with the best possible sound, none of these are the perfect tool. CBT is a much more appropriate tool. I really would like to build some DIY CBT designs that are small, just 6-8 drivers based on 2" or 3" drivers in compact straight enclosures and shading. I already told Mike about the project idea, but I just need to find some time to measure a 3" driver I have 6 of so I can make sure that my crossover models will match real measurements and give me the desired shading and response. The design requires tank filters and padding resistors along with parallel-series wiring of the drivers to obtain the desired flat on-axis response and polar response of a CBT.