Originally Posted by
icyclist
"I can spend most of the day on the 39t middle ring, with almost no FD shifting"
and
"On the other hand, the compact is simpler"
You can only pick one of those, Peter2.
"I like the close gear ratios on the triple"
Is this true, though? I've seen it stated many times on BF.
Look at the Sheldon Brown gear calculator and plug in the numbers. The percentage of the jumps between cogs on the cassette is exactly the same, with either a standard 52x39x30 or a compact 50x34.
The compact acts to, well, compact the range of gearing compared to a triple, by loping off the top and bottom end.
If the same range of gearing is provided with a triple, the cassette can have closer cog spacing than a compact. That should be obvious. For example, if a 53/39/30 triple has the very closest spaced 12-23 cassette (12-13-14-15-16-17-18-19-21-23), a 50/34 compact would need an 11-26 to cover the same range. The 11-26 would be 11-12-13-14-15-17-19-21-23-26. The triple's cassette has seven 1-tooth shifts, compared to four with the compact's cassette, plus the 11-26 has a larger jump at the 23-26. The compact does have a tiny bit of extra top gear, but it's as close as you can get without resorting to a 49T big ring.
If you put a 50/34 in place of a 53/39 with the same cassette, you lose 6% in top gear but gain about 13% at the low end, for an overall increase in range.