Welcome to THE SHOWDOWN, where I compare different types of tanks and mecha. Let me start off with the lightweight division.LIGHT VEHICLE DEFINITION
A light combat vehicle does not have firepower or armor as its main requirements. Rather the goal is mobility and ease of deployment.
Light combat vehicles are often infantry carriers and are armed with fairly light guns (12.7-30 mm) and usually with anti-armor missiles.TANK VS MECH COMPARISON
Smaller mecha are often depicted as fulfilling the light armored vehicle role on the battlefied. One thing that many of them have in common is that they carry jump jets, enabling them to serve as combination gunships/light combat vehicles. At first this seems like an attractive package-A LAV-25 and Apache all in one. But there are many flaws to this design.
One flaw is availability. After all, you can have a light combat vehicle and a gunship, or an all-in-one mecha. The mecha can only be in one place at one time, while the combat vehicle can be on the ground supporting the infantry while the gunship flies around looking for targets at the same time. If armies were equipped with mecha that could do both, they would need to either:
Field huge fleets of these mecha, designating some to stay on the ground and others to stay in the air, or have the mecha be shifting from ground to skies very quickly. Adopting the latter would put tremendous strain on the pilot and mecha, while if you chose the former you might as well use conventional vehicles.
Another flaw is training. A gunship and ground vehicle are meant to carry out very different roles, and you would need to train pilots to do both of them. A pilot trained like that would not be better in any one theater then a crewman trained in a dedicated vehicle. They would be able to go on the ground and in the air, they just won't do it very well. And training can be VERY important in combat.
A third flaw is in the design of the mecha itself. To be a light combat vehicle and gunship at the same time it would need to carry what it needed for both roles in one hull-the jump jets, fuel for the thrusters, flight guidance systems, etc...., which could be replaced by more armor, weapons, or sensors on either a dedicated ground or air vehicle.
And even if mecha stayed on the ground, they would still be inferior to a light combat vehicle of the same tech level, because of the inherent weaknesses of mecha (Tall profile, complex drivetrain, inability to carry large conventional guns, among others).
So in short, a mecha is not as suited for the light combat vehicle role as a conventional wheeled or tracked design.