Mcgonagall was a little better at teaching...Tonks job required dueling/fighting almost everyday.

McGonagall has the experience and she can duel as seen in the books, but the question is a little unfair as there is a big age difference between them.

That was a hard choice they're both skilled witches but I went with Tonks because she is an auror which means that she Duels on a regular basis while McGonagall who is still really amazing probably wasn't as in practice as Tonks.