IMHO, I'm not a fan of compact doubles with a 16T or larger gap between rings. Depending on my bike, I either ride a standard double with a low gear of about 38-39 gear inches (with a 39 chain ring, with a 27 or 28 cog) or, on my bikes with low enough gears for serious climbing (below 30 gear inches), I ride a triple - with 9 speed index in the back.

But a couple of caveats: On my bikes with triples, I use downtube shifters, with friction shifting in front. I find it works better than index shifting on the front (I do use index shifting on the back 9). And I know how to tweak and adjust the drivetrain so that it all works properly. Personally, I think that if you need a low gear in the low thirties to as low as the mid 20s, a triple is the way to go to get that low gear while retaining reasonably tight spacing in the normal riding range.