It depends on your needs. Both wetsuits are well suited for competition and both are the same thickness. They are however made from different types of neoprene.
The MK3 Elite is made from Yamamoto neoprene and the MK2 Comp is made from Jako neoprene.
If you want the maximum advantage then the MK3 Elite is our most flexible and most buoyant wetsuit. It has Aerodome panels (neoprene that contains small air pockets) on the chest and thighs which gives it extra buoyancy.
The MK2 Comp gives more than enough buoyancy and flexibility but is more durable and therefore more suitable for higher usage.