Got a question for you, /vp/

I want to transfer my Dragonite (Currently on SS) over to my White 2 to put him in my current team (And possibly X and Y in the future).

Thing is, he's EV trained but not max level. If I migrated him over to White 2 before getting him to 100. Would it keep the EVs and give me the same stat boosts with every level up?

Or am I better off getting him to 100 on SS first?

Thanks in advance, sorry if it confuses you.