The steps on Metolius 8 Step Ladder were the perkiest we tested. They really stayed open, which made it easy to fish your feet in when moving onto a piece. Metolius uses "Biothane Step Stiffeners," which is a rubbery urethane-like material put on top of the steps. It makes the steps more comfortable on the bottom of your foot and keeps the aider from squeezing the side of your foot. It is very comfortable, second only to the Yates Big Wall Ladder, and not by much. The ladder style is very intuitive to walk up, especially for beginners. After teaching someone to aid with the Metolius 5 Step Aider, Chris McNamara switched to the Metolius 8 Step Ladder and the person had much more success.
While this ladder aider could be easier to top step in (see below), it does have a generous grab loop, which is nice for balance and sliding your foot in for "super top-stepping." Also, this aider is relatively light, especially if you chop off the bottom step like Chris does (he likes a shorter, less bulky aider unless he is doing hard aid.)
Without a plastic spreader on top (like the Yates has) the upper steps get squished together. This makes it less efficient to walk up the top steps. You have to turn your foot sideways and wiggle it in. This is not a deal breaker, but it does make it a little harder to use. We have not used this aider a ton on walls yet and will report back here after using it more.
This is a pretty versatile aider. It works well on hard aid but is also light enough to work on walls with free climbing, such as The Nose (especially if you cut off the bottom steps as Chris does).
This is a great value. It scores up there with the Yates Aid Ladder but will cost you $22 less for a pair.
Metolius 5 Step Aider