The caveat is not having dedicated knobs for params and only 3 at a time so you need to page around like on the HX Stomp.
That's an issue with all L6 devices apart from the Floor/LT/Rack.
But it's not only that they could offer more knobs (ok, the HX One possibly less so), the main issue I'm having with all of them is the parameter "sequence" layout. It just makes no sense and they missed the opportunity to address that on the HX One yet again.
Example #1: When dealing with a drive pedal, regardless of the overall amount of parameters exposed, once you're past the initial setup (which you usually do with plenty of time on your hands), I'd bet every amount of money that 90% of any finetunings involve gain and level (as obvious as it is: you usually need to compensate level when adjusting the gain and possibly vice versa, too). With each 3-knob-only HX family unit that requires page-flipping already.
Example #2: When dealing with reverbs and delays, regardless of the overall amount of parameters exposed, once you're past the initial setup (which you usually do with plenty of time on your hands), I'd bet almost every amount of money that 70% of any finetunings involve mix adjustments. Within the HX family, for pretty much all delays and reverbs (minus, say, the simple delay), "Mix" is parameter #5, hence not accessible on the first page of any 3-knob-only unit.
(The latter is as well true for all modulation units with a mix parameter, but it might not be as relevant here.)
IMVHO this is a major UI design oversight.
And regarding the HX One, as much as it's a major improvement over its predecessor M5 technically, this is a big step back as the M5 (the other M-series, too) exposed 5 parameters, mapped straight to 5 knobs, ready for instant access. One of *the* most appealing aspects of the M-series (and the very reason I was a pretty happy M13 user).
I've said so multiple times already, Zoom is getting that issue just right. Most important parameters can always be found on the first page. Why not adopt that? There's no plausible reasons (and for those prefering the current layouts: of course that should be made optionally).