All these numbers are subject to change with updates and such, but generally should be close. Pretty much all mods will have similar findings, as structure hp is based on the material and it's hardness (which isn't a number I can find anywhere). So Brass and Bronze will amke something extremely close to steel in terms of HP, but add more beauty and obviously cost less since they're made of copper/tin and copper/zinc.

So far Bronze, Brass, nd Plumcalcum seem to be the best. Should be 180/190/170 hp for a shredder turret from the one security mod. Steel is I believe 200, so you don't lose much by using alloys. Infact you save about half the normal cost in steel. Obviously things like Modarium (whihc I haven't unlocked) plasteel, and especially titanium, work too. They are going to be more hp than steel by far. The same works for the normal turret and it works on the mannable turrets too.
As for doors so far only titanium actually is 'better' because it has 200% opening speed. All the alloys (even light weight ones) will not make an automatic door at normal 120% speed. All metal seems to make doors, both auto and normal, more expensive to make and slower. Just like bricks. They do give the doors TONS more hp though.