they are both great shocks
i like the losi's better but use the jammin ballends and spring retainer on them. the losi spring retainers punch out over the ball end to often for me. the jammin ones are heaps stronger
the losi's dont have a nut ontop of the piston so you get that little bit extra travel over the length
but its easier to remove the nut off the jammin's to replace a piston. the .05 screw on the losis can be a pain in the a' to get out if you strip the head
Also the Losi ones are prone to having the screw come out if you don't loctite it and allow it to cure...