There are two major problems with the cheaper ETX models. The first one is the plastic motors that are prone to breaking down and noisy. The second one is the flimsy, cheap, aluminium tripod.
Meade solved these problems with the ETX 125 by using more expensive materials. The motors in the mount are metal, and the tripod is steel. But, as you might expect, this increases the price significantly. Meade ETX 125 is 700$, and ETX 80 is 300$.