The bigger the exp stage, the better, it makes more balance in the game, because on higher levels it is more difficult to advance and people who start the game later will be able to level the playing field more easily.
If it is too low, then there are too big differences between the levels of players and worse fights.
On low rate servers, the fights are the worst, because there are sometimes differences lvl 150 fights vs lvls 60 who has no chance for any normal fight if no make trap with 10 people to kill one guy lvl 150 lvl.
When the levels are 200 vs 160, the differences in levels won't matter much in the fights.