time to upgrade my really really old duffel bag.

i am torn between which one i should get. i think having a 28" will cause me to over-pack while 26" will force me to be disciplined with packing and hence not ending up with a heavy suitcase.

on the other hand 28" does have that extra room in case i do need it (if i go to cold climate like russia and need to bring extra jacket and boots for example)

any thoughts? do most intl travelers find 26" enough or is 28" the standard "issue" for intl travel for people on this site?