Vegeta should win, but with toyo writing you never know. Gas already stated Bardock was stronger than a low class saiyan and then he got that emotion boost as well
It makes no sense for Vegeta to be stronger than the fusion of him and Goku. Yes sure he is using form one level higher and powered up from training but still.
Gotenks clearly had an edge during their fight. Can also be seen with that mouth blast sequence which affected buu eay more and the subsequent beatdown