Eric,

I ride both a 28's and 32's on two different fixed gear bikes. The 28 is noticeably more nimble, to me at least, but the 32 isn't far behind. Both are Challenge brand open tubulars, which are awesome. The 32 does provide a smoother ride though. I wouldn't opt for puncture resistant tubes. I've tried them and they ruin the ride making the wheels feel heavy and sluggish. If a majority of your pavement is fairly smooth I'd go with 28's. If many sections are bumpy I'd go with 32's and 86 the thorn resistant tubes. Carry two spare tubes in your seatbag instead.