The degree of power is so unknown after Frieza arc that you can pretty much believe whatever you want.
Weather it be base Saiyans<120mil or Base sayains>1bil
I tend to think personally 1 bil is way too high of a peak for a Base Saiyan.
If I wanna go my highest id put it somewhere in the low hundred millions.
All in all Vegeta's gains between cell games and Buu arc were just enough to make him a little stronger the cell games Gohan. Who was 2x (or so stronger than him) imo.
If I could chose I'd say Piccolo.