You raised an interesting point--why is it that F15EX can carry almost twice the tonnage of munition as the Su35? It's probably because the SU35 doesn't use enough lighter-weight composite materials and its various other components likewise weigh 50-100% more than their US/Western counterparts (engines, radars, etc). In other words, SU35 is carrying a lot of "weight," so it's not fit enough to do as much work (i.e., carrying weapons) as the F15. It's like an overweight person who has 40% body fat versus an lean and muscular elite athlete.
