Well as an owner of both, I actually agree with you. For comparison's sake I'll compare Vita's launch verse Wii U's launch from a consumer's standpoint.
Vita:
I got my Vita February 15th as part of the $350 pre-launch bundle. It included 4 gb memory, Little Deviants, and a case. Also bought Uncharted Golden Abyss. As an Uncharted fan I loved it to death even though most people only liked it. Because of that I'll act like it was only an ok game, for the sake of being fair. A couple weeks later I bought a 32gb card, wipeout, and a few PSN games. Loved it all, it was great. Then came the drought till Resistance where I didn't buy a single game. Heck I didn't touch my Vita too much during that time. After the drought though more games started coming and it became great again.
Wii U:
Oh I'm not really sure why I bought my Wii U. Unlike my Vita I wasn't counting down the seconds till it was in my hands. A week before Christmas I saw a deluxe edition and just spontaneously bought it along with NSMBU and Zombiu. Turns out I actually really liked it. I do have to admit something though; this was the first time in my life I've ever really played 2D Mario. To be honest it's over rated and 3D Mario is a million times better. After the first couple of levels it became a chore to play instead of a treat. Right now I'm stuck in that Boo water ghost ship and haven't touched it for weeks. ZombiU was a lot better but it's just a normal Zombie game. I enjoy it but again I haven't touched it for weeks. Dieing and having to restart so far away makes me lose all desire to keep playing. Nintendoland is my favorite. I don't specifically love any of the games but I really have a desire to unlock everything. That Planko game is addicting and keeps bringing me back. Well, maybe once a week back. My Wii U is right next to my PS3 so more often then not I find myself playing it again. I don't plan on buying another Wii U game till Pikman 3.
If you bothered to read that, good for you. Now I'll get on topic ;)
The Wii U will never outsell the Vita. Thinking the opposite is only the result of trying to reflect last gen Nintendo onto current Sony and its desperate situation.