For me, I'd go with at least the 27. 30T isn't all that small for a triple--inner rings used to be smaller.

If you can shoot for 1-to-1, especially for big hills and/or weight onboard, you can't go wrong. That could be 30x32, instead of 30x27, but you might need a biike mechanic to get the 30x32 working properly (there might even be a few mechanics that say it cannot be done because, as said above, it's not suggested in the Shimano manual, but it does work, in my experience, on both Ultegra and 105 9-spds).