Originally Posted by
FormerFF
Most of what you'll be looking at has what's called a "compact" crankset, typically a 50/34 chainring. Shimano equipped bikes usually have a 12-30 cassette, while SRAM Apex bikes often have an 11-32 cassette. Most road going triples will have a 30 tooth small chainring and a 30 tooth big cassette sprocket, so you're not giving up much to that triple as far as ratios go, and you're saving a little weight, have a narrower crankset and less duplication over your gear range. Plus, I think the two position front derailleur is easier to deal with and shifts more reliablythan does a triple. If you want lower gearing than that, you'll have to go to a bike with a long cage derailleur, like a touring bike.
Keep in mind that the 30 tooth ring on a road triple can be easily changed to a 28, 26 or 24 tooth ring for even lower gearing. A compact double can't touch that. I'll never understand why 30 is the standard for road triples.
Duplication of gear ratios is a good thing. It means you are more likely to be able to find the next lower or higher gear using the chainring you are in rather than needing to make a front shift.