I am having 1400 sq. ft. slab poured for my 34 ft Motorhome to sit on I have had some contractor say use fibermesh and some use reinforce steel and some say both what should I do.

It will all be about the weight of your motor home. The weight of it will dictate a) how thick the concrete should be, and b) what sort of reinforcement is used.

My thought would be that steel (rebar) will be best, but beyond that there would still be the question of how thick the pad should be.

What is the weight of the motor home?