Haven’t tried Ultra but have used both Soft (1.25 & 1.20; Black) and regular Hex (1.23 White & Black & 1.18 Black). IIRC Focus Hex Ultra is similar to Focus Hex Soft, maybe a lil crisper. Focus Hex Soft has more pocketing/plushness obv but both strings have great durability & tension maintenance, even in the thin 1.18 & 1.20. Spin varies across the lineup but so far the FH Soft 1.20 Black & FH 1.23 (both white & black) have been the best for me. Also as you may know string colors affect feel. EX: white FH feels more metallic & crisp, where black FH has a bit more ballpocketing and feel. Hope this helps
Focus Hex is not predecessor of Ultra, is just a bit more control-oriented, while Ultra it seems to be a tad more powerful (closer to Focus Hex soft): MSV Tennis Strings - msv-tennis.com
Just tried Hex ultra (black) 1.20 and I prefer the hex soft more. The ultra version seems to be thicker than the soft and adds more swing weight. Its supposed to have a slick coating on it which maybe it does but it’s not apparent in the playability. It’s only the initial hit though so I’ll need more time but if I had to choose I’d pick the hex soft.