Definitely pot. As others have pointed out, it's more socially acceptable, carries much lesser legal penalties, is relatively easy to function normally on, etc. It's also cheap, and I already smoke often enough that needing to smoke regularly to feel ok wouldn't be that big a deal.
I'd consider opioids, but IME they work best as an occasional thing. I wouldn't want to lose the ability to enjoy an opiate high due to excessive tolerance, anyway.