What I got for my area in NE Pennsylvania is the SRAM 11-28.
The wider the gear range the better.
There are enough gears in a 10 speed cassette to ensure no excessive gaps in the 11-28 for me.
Of course, with it, and the 50/34 crank I needed at least a medium cage RD according the the LBS, I believe for the chain wrap.
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Slow Ride Cyclists of NEPA
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