There's a thread on here somewhere about it. Check Suppversity - I think there are now at least 5 *recent* studies on HMB-CA showing positive outcomes for athletes at just 3g/Day. I just got another Kilo in for about $48 - good for another year
The Free Acid (-FA) is a lot more money - maybe better for an "over-reach" (but maybe not, I forget, check the above studies), but -CA as a staple is a no-brainer for me.
I was taking HMB-FA for ~1-2 weeks (after this past semester ended) now that I'm getting to the gym more frequently, and switched to HMB-CA powder when I ran out of the HMB-FA caps I had left over from the last time I ran it. My dosing is 3g of HMB (whichever one) pre-workout, and just whenever on rest days. So far, the CA seems to be doing just as well as the FA (I'm lifting ~6 times per week, hitting each muscle group 3x per week). If you're a guy who likes high volume and/or frequency, it's a very nice supplement IMO. If you're just going to half-a** workouts and/or only work each muscle group 1x per week, it's probably not going to do much for you though (conditionally beneficial IMO).
If I had to pick 3 supplements to run consistently (for muscle/strength/bodybuilding purposes, not nootropic/general/etc):
-CreMax XT (basic staples such as creatine, betaine, etc)
-PA (lecithin granules; no need to get too fancy, and I can adjust the dose. I like ~3 tbsp)
-HMB (FA caps if price is no concern, CA powder otherwise)
>(Ergonine is also great, but I prefer HMB to HICA, and don't see additional benefits with both)
>(Triumph is also great, but I don't mind granules, and like the freedom to dose higher if I want)
> (you really can't go wrong with CreMax XT, Ergonine, or Triumph as a staple/base
)