I find that each rope grab has it's advantages and disadvantages. It depends
on clean, dirty, wet, dry, material, weave, etc. Ultimately I just have to
try a particular hitch on that rope. i play around with Klemheist, Hedden,
Bachman, Prusik, Penberthy. The Klemheist/Hedden variety is my favorite.
Any of those are tough to use to get over a lip. Lots of luck! Watch your
knuckles. I use a frog system for caving. For pothole escapes I like Tiblocs.
They are a reasonable compromise between simple hitches and metal devices
used for caving. Depending on rope diameter and size of carabiner used, they
make it much easier to get over the lip.