The original Gillo C88s had an "advanced recurve" profile that was designed to optimize smoothness to 5% per inch over a wider range of draw lengths (or a wider range of preloads). This was designed in conjunction with W&W and used on their MXT limbs as well. It's not quite a super-recurve (even a mass produced super-recurve like Uukha), but it does store more energy and is smoother at full draw.
This draw profile is also found on the Q5 and Q7 limbs, which have varying ratios of fiberglass and carbon, unlike the C88s which are all carbon. The C77s have basically the same curve profile and use a simplified core structure compared to the C88s (fewer layers) which is a little more durable but is also lighter. They're also a little more tapered IIRC. This results in a limb that is faster (the C88s are very stable, but were a little slow compared to even similar limbs like the more expensive MXT series).
I haven't seen or used the new Alphas yet, but in general Uukhas' super-recurve profile is more extreme, and narrows down to a much smoother draw force curve (3.5% at one point). This means that they have a smaller adjustment range when using the tiller bolts or floating limb pockets. They're also heavier at the beginning of the draw (so are C77s when compared to conventional limbs, but not to the same degree). I found that I really liked the way Uukhas felt to shoot, but that I shot better with a limb that was less smooth (while still being smooth).
The W&W MXT limbs were a happy medium that performed just as well in terms of speed (Uukhas are "faster" with the same arrow, but need a stiffer and heavier arrow so the actual speed for a tuned setup was comparable for me), but felt more stable. I've shot all of my personal bests with those limbs. The C77s are very similar in feel, but much cheaper than a new set, so got some when I wanted to try medium limbs on a 27" GF riser for the upcoming outdoor and field season. They are very similar to the MXTs that I have been shooting, and they are noticeably snappier than the older C88s. That means that they're a little louder and vibrate a little more, but a set of Rigi limb dampeners cleaned that up without an appreciable loss in speed. I was able to use the same crawl marks out to 60m as I used with my 25" GF and long MXT-10 limbs.
If I had a very short draw length and was shooting a conventional riser, I might prefer Uukhas. But on a riser with floating limb pockets, the Gillo limbs let you dial in the draw weight you want while maintaining similar levels of smoothness and stability. For long draw length archers, the combo lets them dial back and avoid the stack point of limbs where they lose efficiency and smoothness.