I have both a
Seekins low profile adjustable and a
Syrac Ordnance Gen II block that I purchased through JPRifles.
For field switchability, the Syrac is better suited.
I say that for two reasons:
One - because if you are tucking it under a hand guard, the adjustment screw is out the front (you'll need a long allan key to reach it then).
Two - the adjustment screw has 'clicks' much like a scope knob. You can easily count the number of clicks as it is a very tactile click. I use it on my 300blk build and I know where my adjustments are for both suppressed, unsuppressed, and with super and subsonic combinations.
The seekins block is just a continuous screw witha set screw. Sure you could count rotations, but the lack of clicks makes it more guesswork. I use it on my 10.5" 5.56 which I never shoot without a suppressor (because it is brutal without it). I just wanted the ability to squelch the gas down as much as possible when using the suppressor to eliminate as much crap blowing back in my face as possible. So it has a more set-it-and-forget-it use.
I would buy both blocks again for their intended purposes.