To contradict all of you'r posts here saying that Aluminum is weak, my case front door is almost bulletproof and this case is very durable (It kinda slipped from my hand first time I took it out of the bag it came in....I was sure its broken to pieces but its actually scratchless ^^
Also, SECC Steel is very heavy compared to aluminum, and usualy cases made from that material didnt go through a folding process in which they fold the sharp corners etc, not healthy for you'r fingers! ^^; almost every aluminum case out there (sides the low-end ones) goes through this process to make it more safer to use (no more cuts after opening you'r case for modifications! XD)
and thermally, Aluminum gets heated up faster, but it also gets cold much better, thus its heat transferring is much better than SECC steel.
Cons is that it is maybe 2-3% less durable than SECC steel, but if you drop a SECC-made case from big hights it will break just like an aluminum made case, same about if you hit it or put alot of pressure on it.