Trade-offs. Do you want to be fast or stable? In here the stability loss is "only" 5% (doubled for dodges), and the design doesn't have JPs. The occasional charge, BRG hit, or big leg hit, but no DfA checks, or airborne hits. Still, it's a CC titan. The MLs do have some range though, and they are mounted on the arms, so it's a good alternative.
The heat diss and cost improvements are minor (so is the slightly higher max climb), the real advantages are the BMT, extra internals on the arms and legs, and smaller heat reg.