Lower geared cassettes - Century Special vs. custom Miche
I'm considering lowering my bike's gearing. Currently using a 50-34 crank with 12-27 cassette, and an Ultegra 6600 10 speed drivetrain (except for the compact crank).
I have narrowed down the various cassette options to the 9 speed Harris Century Special (13-30) or a 10 speed custom Miche cassette (13-29; to acheive this, I'd get a Miche 12-26, remove the 12, 13 cogs, add a 13 first position cog and a 29 last position cog).
Both should work with an Ultegra short cage derailleur in terms of max sprocket. Even with a 27t cog, the B-screw is pretty far unscrewed, so I think there's enough adjustability to fit a 30t cog. And the Ultegra short cage mech should be able to wrap enough chain for my setup (needs to wrap 33t to use small-small combo), but I avoid small-small anyway.
Pros/Cons of the cassettes (relative to each other):
Pros: lower gear; pre-built
Cons: if 10sp shifter doesn't shift the 9sp cassette crisply, I'll need to either get a Shiftmate or a 9sp right-side shifter
Pros: 10sp, so shifting is likely to be great; gear spacing
Cons: limited to 29, which is not a huge jump from existing 27
I decided against mtn cassettes because the gear spacing is too wide, and I'd rather sacrifice an 11 or 12 cog than lose middle cogs. Similarly, the IRD 10sp cassettes are too wide and have small cogs I don't need.
Anything I'm missing? Thoughts?
As with so many things two-wheel-related, my understanding of the topic has been greatly augmented by Sheldon Brown's excellent articles.