>>You are right about the low siloette but a tank cannot crouch behind a hill. pop up for a second and crank a round off before hiding again.

No that's why the military combine current classic operational advances with attack helicopters like the Apache. Walking mechs are a nice concept but the lacking technology would probably be the ability to create a sufficiently recoiless main armament not to knock it on it's arse when it fired. That's in terms of realistic technology available today, not in the future.

>>The advanages to a mech is speed, better terain ability and a more steay barrel.

MBT's are currently fairly speedy and tracks move faster than legs. While the terrain point is well made it is unlikely the barrel would be more steady under current design parameters than on an MBT. But you don't need one vehicle or combat machine to do everything, trying to do that is a noticeable feature of some WW2 German tank designs that never got off the production line. The Romans perfected the idea of using combinations of assets to win battles and modern armies are no different - one size does not need to fit all.