In this fusion, Vegeta is the dominant influence. He is second only to Broly in power. Vegeto is able to hold off Evil Buu with ease, as a normal Saiyan (as apposed to a Super Saiyan), until Evil Buu transforms into Super Buu.
Due to Vegeta's influence on the character, Vegeto is often pertrayed as cocky, making the same mistake as Gohan in the Cell Games. This cockiness leads to Super Buu almost tearing apart the fabric of time and space.
The fusion earrings used to form Vegeto is the "proper" way to do fusion. So, the resulting fusion is of higher quality than the common Fusion Dance, meaning the end result has a much higher power level.