Another good point, if you use heavier strings, you may have to widen the slots in your guitar's nut. Allan's point is well-taken, but I think it would not apply if you change your strings often. Older strings become harder to tune because they lose their uniform thickness (by wear and from accumulation of grime between the string windings), which would of course vary in different areas of the string (the places where you touch them, and the places where you don't). In the really old days, players of gut strings had to adjust their fingering for each new string, because they pretty much never had uniform thickness to begin with.

Again, good luck, Chet W.