I've got my filco rest for a few months, and no signs of wear (but that means nothing considering how short a time it is). I don't have the other rests that are in competition, but i can say that the rest being stepped is a feature that should be considered. When i was making the purchase i was wondering about the reasoning behind the design of the two heights, but i was unable to find too much information concerning it.
From my few months of use, one of the biggest advantage is helping my hand find the correct distance from the keyboard without looking down at the keyboard, along with the two nubs on the F and J keys, this allows for accurate placement of your hand without needing to look at the keyboard, and i think it serves as a pretty good guide to ensure that my typing posture is correct. Personally for me i thought the height was slightly on the low side (used with HHKB), and i elevates it slightly by 2 mm.
After playing around with it, i am pretty sure the two heights are not for flipping the rest around for taller keyboards, the distance just doesn't work.
Thing that irritates me, i line up the right side of the pad with the right of the keyboard, and my right palm rubs against the filco logo whenever I reach over to the (fn+ arrow keys) and you can definitely feel the logo there.