u will get advantage in cross server event like SWB (the top reason why people does freeze their level) and fighting matsuri.

u will lost many free stuff in server event though , like coins from ninetails, reward from doing daily activity and weekly mission (it will be deleted though when 4.0 patch come), weekly event cycle which require u to claim dailty activity to get the reward, eg. sakura blessing event, balloon, etc. U will be a weakling in ur server but will be a king in swb :). being first place in swb ranking can give u 15 advance refine rune, seal scroll as extra reward.

Your choice :)