All Burtons are all plastic. Same as K2 and Flux. Its not a bad thing. But Honestly I think the SL's are a better binding than the Cartels. I don't know why he said they were lighter, they shouldn't be. The foam is the same, EVA, but the Unions may be a "higher" quality EVA. You also have to take into consideration the stock forward lean of Burton.
I would say as far as performance, if you're going to be jibbing a fair amount the Cartels will be painfully annoying. If you're doing mostly freeriding, both will give you good performance but the Cartels might do a fair bit better.
Go ahead, drink that kool-aid.
FS: Forum Sauce 142 $200 plus shipping
FS: Flux SE30 $75 plus shipping