Otterbox vs. die-cast aluminium

[Lomax]

While a tubular or spherical shape of course will handle pressure the best, I've seen a lot of people recommending using an Otterbox for their electronics compartment, and that makes me think a well sealed die-cast "project enclosure" might be suitable as well? In particular I've been looking at the sealed enclosures made by Gainta, which although only rated IP67 seem a lot sturdier than the usual die-cast boxes. I'm thinking that with an additional rubber seal (cut using the lid as a template) they should be completely watertight - but will they withstand the pressure? They are relatively cheap, and it should be easier to make watertight bulkhead connections than with a plastic case - though the main attraction is their ability to act as a very efficient heatsink. If anyone experienced reckons it could be worth a shot I'd like to test one by lowering it to 10-20-30 meters and check if it remains dry inside. Any thoughts?