Difficult to answer.
I like CustLemm as it is the original way to play the original Lemmings levels made by fans with the original graphics sets. And now, it is possible to make our own special graphic levels.
Cheapo is good too, but isn't the "very" same thing. For Cheapo, I think we pass much of the time to make our own graphics, traps and lemmings instead of building the levels. Also, the editor isn't easy like LemEdit and doesn't have an Undo feature where it could become very annoying. But the fact that we could make everything possible is really cool!
So, I don't know... Both are good, but I think I would prefer CustLemm and LemEdit because it's now the only editor I worked much of the time with.