It really depends on your terrain. I have triples on all 2 of my road bikes but the chainrings different sizes as are the cassettes. The bike that gets ridden in the biggest mountains as a 11-32 cassette with widely-spaced cogs. The bike that gets ridden around home where it is very, very flat has a 14-25 cassette (Bubba's is 12-23 for his) so I can get very small 1-tooth differences. If I only rode the flat roads around here I wouldn't even both with a compact double; I'd stick with a standard double of 39-52.

Your choice of gearing should always be based on your terrain and ability, and the best examples are to look at what your local peers are using.

If you just have one bike, you can vary your gearing for a specific ride by just swapping out the rear cassette. You just need to have the rear dérailleur and chain adjusted for the larger cassette.