I'm on team natural fiber but the team synthetics people have a point about cotton's downside.
So, when something that can please almost everyone comes along, I think it is worth mentioning:
Banana Republic has something called 'slim fit linen blend five pocket pant' and the description details warn that it runs small. I don't like the tapered cuff look that has been popular among non-old men the last year or two, so here's the trick:
buy a longer length and hem them -- you end up with a very nice looking pair of slacks with a non-constricting rise.
Half linen and half poly with a pinch of spandex, such that it folds down to half the packing size of equivalent cotton. A little shocking how compact actually, without feeling too gossamer or plastic-y.
Generous belt loops, coin-catch pocket inside right front in addition to jeans-style fifth pocket, and deeper than Columbia (why does Columbia have such shallow pockets?) In dark colors it could pass for dinner or evening activities.
If you're not in a rush and sign up for their spam, you can find most of BR's stuff at 70% off every month or two.