My experiences with all three:
KB Goblet Squat - i like these as a warm up, to pry open the hips. Difficult to load these up vs. DFSQ or Zercher. I like to add pauses at the bottom to increase difficulty.
DFSQ - These light up my core big time, especially in the 8-10rm range. I don't have double KBs beyond 16s, so I end up having an uneven load, 20/24, or 24/28, etc. I've used these in a hypertrophy cycle (BuiltStrong), but haven't used them in a strength program.
BB Zercher - These are my 'go-to' heavy squat. I do not have a rack, so I either zercher from the floor, or I have the bar boosted up (24") on my two pyloboxes for the setup. I personally love zerchers for a few reasons. 1) great recruitment of the upper back, 2) super safe movement if you need to dump the bar, 3) minimalist setup (literally just a bar and weights needed). I'm tall, with long limbs, so I find Zerchers more comfortable vs. front or back squats.