Right... to the original issue, no. That's not how percentages work ... 110% of A and B does not change their relative values at all, they are still A n B, just 1.1A and 1.1B. The niches for mediums are:
Std engine (kinda forced on Hunch, and so awesome with the Cent it is very very very good idea)
Cicada 120.3-129.2kph at 17.5-14.5 tons of payload
Bjack 108.9-118.8kph at 21.3-17.8 tons of payload (if engine ratings allow it)
50tonners 96.2-106.9kph at 27-22.5 tons of payload (Hunchback is so out of luck, sorry)
With XL engine (doable with Trashbucket and Cicada, suicide on Hunch, on Cents well it can be made to work a bit)
Cicada 142.6-147kph at 19.5-18.5 tons of payload
Bjack 128.7-140.6kph at 23.8-19.8 tons of payload (again if engine ratings allow it)
50tonners 108.7-128.3kph at 30.5-24 tons of payload (again, Hunchie is SOL)
HOWEVER Dragon can pull 106.9kph at 33.5 tons of payload with XL, so going low speed XL on the 50tonners is realllllllly not a good idea.
As Dragon ain't bad with an XL, you pretty much have to push the boundary if you go medium n XL, meaning Cicadas or the fast Trench/Cents. Ofcourse Hunchback variants tend to lose such a huge amount of their weaponry to losing the side torso, one could argue that just dying then isn't THAT big a loss. =P
But the mediums do have their place in the payload/kph spectrum. Cents are huge but damn can they take a beating with a STD engine. Other's I have only played against not with, so can't say bout them that much except the above notes.
edit: with endosteel and speed tweak taken into account, as those are near ubiquitous.
Edited by Nipsnaps, 19 May 2013 - 02:12 PM.