Of course you’d follow the wife.
A wife following the husbands minhagim isn’t as halacha lemoshe misinai as people think. It’s a relatively recent question. R’ Moshe says it’s like she’s moving to his locale so she adopts his minhagim. If he doesn’t have minhagim there is no reason he can’t adopt hers.
(Some minhagim are older and more defining of segments of jewry and perhaps this wouldn’t apply , for example kitnitos which even if an Ashkenazi doesn’t know his minhag, we do)