Thanks everyone for the detailed and professional response.
CR-01 : I love it due to the appearance and shell, but really think it is not very good at crawling
Kyosho : I love its mechanics and it looks sturdy, but it is less popular and so parts/upgrade may be an issue
AX10 : Seems popular, simple in structure, no worry on parts
For the Creeper, I think it's like standard AX10 but part availability might be a question!
Also I heard the Creeper has problem as some parts too easily break down and the center gearbox is too large and heavy in comparison with the AX10's one.