Be it, difficulty to use, make a viable build out of them or simply how hard it is to master them. For instance its harder to master atlas because of their cost unlike jenners. But this is all subjective, you can give a low score for your own reasons, but we love to know why.
So, let me start! (you can simply copy and paste my list, then change the numbers)
(1 is very easy, and 10 is very hard to use.)
lights
locust-------------- 10/10 So light that you can't make a difference, die easily, no jumpjets.
commando-------- 9/10 Very light, barely make a difference, die easily, no jumpjets.
spider-------------- 5/10
jenner-------------- 4/10
raven--------------- 6/10
medium
cicada-------------- 8/10 Nothing a jenner can't do, no jumpjets, not enough speed.
blackjack---------- 6/10
centurion---------- 4/10
hunchback-------- 3/10
trebuchet --------- 9/10 Way too big.
kintaro------------- 8/10 Too big and not enough tons for heavy armaments
shadowhawk----- 2/10
heavies
dragon------------ 10/10 center torso is constantly exposed, torso twist is null.
quickdraw--------- 6/10
catapult----------- 5/10
jagermech-------- 1/10
thunderbolt------- 3/10
cataphract-------- 3/10
orion--------------- 5/10
assault
awesome--------- 10/10 Low speed, no ballistic, wider than a barn
victor-------------- 2/10
battlemaster----- 3/10
stalker------------ 3/10
highlander------- 1/10
atlas-------------- 4/10
Have fun!