Don't discount the value of a "puncture resistant" inner lining. I've been riding a set of Bontrager Hard Case tires with a similar lining in about 3500 miles on those tires I've had 0 flats, none, zip. I've picked glass out of the tire, it's cut and chewed from glass and debris. Now, I'm not a huge fan of the Bontrager, they roll like rocks. But that liner has saved me from numerous tire repairs. I think for a "training" tire or an "everyday" tire, something with a liner is IMO a "must" or at least a "very nice to have". My next set of tires will be Conti Ultra-Gators.

For those who don't know the "liner" is a fabric material, probably nylon or something (heck, maybe even something fancy like Kevlar) that resides between the outer rubber and the inner part of the tire. If/when something cuts through the outer rubber the fabric often stops it cold. Maybe something sufficiently small and needle-like could get through but in my experience it's pretty impervious to everything you'll find out there.