36v vs 77v comparisons pros & cons?

I see everyone recommending the 36v versions of the cree COBs, but i see there are 77v versions too. There are a few mentions about them throughout the forum, but n one really seems to be using them? Is there a specific reason why? Less efficient? Drivers not as easy to come by? Just interested, trying to do my research but i've being totally overwhelmed by data sheets and real world results on these forums. It's just all quite hard to fall by because there isn't one specific place to compare, nor is the data complete in some cases (Supra and friends have clearly been extending data sheets and experimenting).

The 36V version is twice as wide as the 77v, and the 77 is twice as long as the 36V.

The 36V version would be good if you wanted to put a bunch in series since you could get twice as many in series given the same max output voltage of your driver.

The 77V can use a lower current driver, and thinner wires.

I once said that the 77V one seems better, but I now think the 36V ones are better since they balance the parallel chains for you allowing you to cram more power in via series combinations without getting to a dangerously high voltage. If you're limited to a low current, the only way to pack in more power is higher/dangerous voltages.