STRC has pretty good aluminum parts from what I heard. But I wouldn't go full out on aluminum for everything, leave some parts plastic.
Aluminum is ok for:
Shock towers
Arm blocks/braces
Caster blocks/steering hubs
Bellcrank/steering rack
Sometimes bulkheads/diff cases
Chassis braces
Plastic is good for:
Arms(!)
Bumpers, extra protection pieces
Steel or Titanium is good for:
Turnbuckles
Aluminum can bend on hard impacts if you crash or get hung up on something, can either bend or send the energy to the part that they are attached to
Plastic flexes and can return to normal, that's why most bashers have more plastics. Especially 1/10 and smaller. 1/8 and bigger is where more aluminum comes in because they are heavier, plastic can warp though, mainly for plastic hubs or anything that holds a bearing. Hence why anything that holds a bearing is nice to upgrade that part to aluminum for extra bearing support/less play.
Aluminum for turnbuckles/tie rods, Yes Traxxas has aluminum upgrades but I would stick with steel rods. Traxxas lies about their aluminum strength and is 99.99 percent likely to snap under moderate-heavy impact. (Ask me anything, snapped like 3 traxxas aluminum tie rods on my rustler)
RPM is a good upgrade for plastics, they are more softer and more flexible, but the modern Traxxas HD/EHD parts are pretty darn good durability wise. Raptor R should have the HD kit already on it from the factory so I wouldn't upgrade much unless it breaks.