Once you master both, you'll have a better command of Japanese than at least 90% of weebs (a rather pathetic stat). And I'll finally have someone to talk about the frustrations of learning kanji on these boards again.
"Ni" is the more common way to say two. There's also futatsu. When you count certain objects, you have to say futatsu. For example, "Oppai ga futatsu arimasu." (There are two tits.)