The Fusion 8's have a very accurate frequency response but they are not capable of full range playback, which means the treble is going to sound stronger than the bass if you don't have them paired with subs. So this would be the first step if you don't have subs....get subs.
Although I haven't seen FR measurements of the Helix Domes, I would assume that they also are likely to have an accurate frequency response as they are also designed by Jeff Bagby. They will certainly play lower without a sub than the F8's so in that regard the tonal balance will certainly be more prominent on the low end without a sub, but should be used with subs regardless imo.
IMO, the biggest difference between the two designs(when properly crossed over to subs) will be that the F8's are a controlled directivity design that limit far off axis dispersion, which of course limits reflections off walls, ceilings, floors. The Helix domes OTOH are more of a wide dispersion design that will have more wide axis reflections adding to the sound you hear.
Personally, I think the one way to tell which design you would like better would be to build a pair and get them in your room and compare. For lower level listening, either speaker would be far more than capable in terms of SPL. If higher level movie listening is your thing, the F8's would pull away the closer you get to reference level due to greater sensitivity, higher power handling, lower distortion, greater dynamics etc.
The Helix domes look like a very interesting speaker to me as well and I think this would be a very interesting experiment to compare the two speaker designs, just wish Jeff would provide some on and off axis measurements as we know this is a very important aspect of how the speakers will perform and sound.