generally run 23's on the light bike because i'll ride up a big hill or two on occasion and every ounce seems to count.
i've run 25's on the same bike and haven't noticed a difference in ride smoothness/vibration dampening quality but
have noticed a difference in handling, acceleration from (complete or nearly so) stops and climbing longer (1+ miles) hills.
double wrapped the handlebars to deal with extra vibration and it works for me. if i know i'll definitely be doing
some serious dirt stretches, i'll rock 25's but my dirt adventures tend to be spur of the moment and i've done 23's where i shouldn't have.
rarely a flat in those conditions but my speed isn't the best.