I was wondering the same. I went for the intelijel and it seems great I've never used the others listed here. Other options are the Tangle Quartet or that Zlob one which is 6 vca in 8hp I believe?

I went for the MI Veils, nothing to complain here. I choosed it because of its layout, each channel on a horizontal line.

I like quad VCAs that have a "separate" sum/mix output like the Doepfer A-135-1 (if you have the room) and the Bubblesound VCA4p (crowded panel but still patchable even with right angle cables!)

Many quad VCAs have a mix output on channel 4 but channels are subtracted from the mix as you patch into them. I like to run all 4 VCA outputs to separate channels on a stereo mixer for panning and then run the separate VCA mix output to processing modules like delay, reverb, Rings, etc