The benefits and comparisons between plastic and metal housings go on forever, kind of like mac vs. PC in the computer world. If you are constrained by $ then Ike is the way to go, but for most people Matt above said it right, I would like to have a Subal but am price constrained. If cost is not an issue at all then Seacam is the top of the line. Next is probably Subal, then Aquatica,Sea&Sea,Watershot etc. As for lenses, the 17-40 or 16-35 are great, the 100 macro is clearly necessary for macro.
The biggest advantage of the smaller, more ergonomic housings is the ability to make fast adjustments on the fly without thinking so the once in a dive opportunities get captured. The quality of the pictures you take won't be different (or barely different) but the ease with which you get them will be. If you can find a store that has some of these play with them. If not make a trek to Backscatter or Reef or H20Photo pros and play. You won't go wrong with any housing, some are just a bit simpler to use than others (and they hold their resale value better than the larger Ike's) at least in my opinion.
So it comes down to budget, if you are constrained then the Ike is your only real choice; the rest are a lot more money.
Bill