Cross-referencing this site http://www.thehi-los.com/recordings/list.php?format=4 it appears that this is, at last, the complete Trend/Spotlite recordings of the group.
Long overdue, and if you like this kind of thing (and I do), essential. This was their freshest and most audacious work, much more cutting edge than most of their later work for other lables (still haven't heard the MPS reunion sides, though, which I hear are excellent).
The Hi-Lo's were what the Four Freshmen were only trying to be. You can take that any way you want to and probably be right, but the fact remains - Gene Puerling's vocal arrangements set a standard of harmonic sophistication in a certain "realm" that has yet to be topped. Take 6 has at times equalled it, but nobody's surpassed it.
You get a lot of other stuff with the Hi-Lo's, and not all of it is "comfortable". But for me, the creativity and musicality of those vocal arrangements trumps all of that.
Mileages on that, however, can and will vary wildly.