I am not familiar with either manuf on the aluminum, but my suggestion..stick with plastic. Plastic will bend and is more forgiving. The aluminum, although it looks nice, will add a lot of weight to the truck and when they get bent are trashed costing more to replace.
Good luck with whatever brand you go with and happy modding/upgrading.
Ill say stay away from alloy arms but if you must don't do any integy stuff but shock springs and brakes. the rest of the stuff is made of soft butter like alloy