i have to say i often play as a light body and i dont think you seem to get as big an advantage as the other body types do am always running around jumping of things climbing like am awsome am awsome and then start to shhot a guy before he is mowed down with a minigun to the left of me i look to my left and there a heavy just stood there like sup its like wtf dude then a bunch more of them how did you get up here to then look and notice stairs its like wtf so everyone can get up here i just look cooler doing it ok am going to find a place only i can get to so after looking for 5 min i find a balcony 3 miles back where no enemy will ever come i do like the sprint bonus because it does help but at the start of an AI game i run of sprinting to then have some heavy guy waddle past its like how are they so fast when there AI it just makes me think the only thing the lite guys get is the fact that they can just do thing cooler than anyone else
Ok, now that I've broken it down into what I think are the various thoughts...
Lights aren't supposed to get an "advantage" overall. they have advantages and disadvantages depending on the situation. I've heard plenty complain that their heavy drops too lights to fast, so it also goes both ways.
That's what heavies and miniguns are for.
There are a lot of places that have long ways around so that heavy's can get there.
There are lots of paths that can only be accessed by lights from one side, shortcuts for you to get to the enemy side, but that the enemy has access to from the other side.
You shouldn't want to out run your heavies on the way to battle, only if you intend to avoid the battle.
Again, the light has many advantages you just have to look for them to see how they benefit your team.