I don't know why SP quit making the adjustable legs; they were pretty nice, if a bit heavy. But to be able to set them up for standing or sitting is pretty nice. The screw-in feet do adjust an inch or two for uneven ground, although there was a post a few years ago about using the Ikea feet for even more adjustability, and with a much larger pad, the Ikea's don't sink in sand as much.
Truth be told, they can be a little rickety... you can never get them tight enough to have things not be wobbly. If you happen to pull them out too far or rotate them while extending, then getting the pegs to line back up again is a PITA.
The Drifta legs are infinitely adjustable and lock tight. If Drifta weren’t so proud of them and the shipping wasn’t so high, I’d replace more of my adjustable legs with them. I also couldn’t imagine trying to do a bigger setup with them. Getting them all the same height would likely be problematic.
So both have pros and cons.
I still use the SP adjustable with my 2U kit since they collapse down to the same width as the unit frames which makes it nice for packing and gives me two options for setup. I also carry the really short adjustable legs in my accessories to make a side table, or for sitting on the ground directly with a very short table. Those aren’t as wobbly.
I use the Drifta legs with my table on the truck directly and another set on my table attached to our trailer. It nice because those two heights don’t line up directly with the SP designated heights.