There's simply no accurate universal benchmark that can be used to compare any fictional universe. You could assert that the entire DC universe is the physical size of an atom in DBZ, and there would be no definitive way to disprove it beyond reasonable doubt. For arguments' sake, let's just assume that the Earth is the exact same size, with similar strength amongst the regular Human inhabitants of them. In the DBZ universe, it is shown that Vegeta can destroy a planet and it's moon with very little effort, at a power level of 18,000 (figure taken from DBZ wikia as his power level isn't shown until later, potentially after training). Now, later in the series, there are several beings whose power level is 1-1.5 billion (also taken from the DBZ wikia). Gotenks and Goku both attained it through the Super Saiyan 3 transformation, which multiplies the base power of the subject by 400, with Ultimate Gohan and all forms of Majin Buu not using any power multipliers to attain that level. Super Buu with Ultimate Gohan absorbed would be at a power level of at least 2.5 billion, and Vegito is able to fight on par with him in his base state, implying he is approximately 800x stronger than Goku. We can assume that he has access to Super Saiyan 2 (100x multiplier), as both fusees have used that transformation. Going into non-canon media, Gogeta is a seperate fusion of Vegito, with a power level of 2.5 billion as a Super Saiyan (50x power multiplier, which puts him at 16x more powerful as Goku in the same state). Now, Beerus is reportedly 100 times as powerful as Goku's super Saiyan 3 transformation, and Whis is more powerful by about 1.5 times that. Assuming Vegito can transform into a Super Saiyan 3, he would be the most powerful known being in the DBZ universe with a speculative power level of 1,200,000,000,000. Generally, beings with high Power Levels have equally ludicrous physiology, and as such can hit proportionally hard with their attacks, and move extremely quickly. On top of that, they generally have great fighting experience, giving them good skill, and problem solving abilities. There are several beings with ridiculous fighting ability, and with unique advantages. Cell, Janemba and Buu, for instance, each need to be completely atomised in order to prevent full recovery through regeneration of Anatomy. Janemba also has reality manipulation ability, which could potentially put him on god tier. Hopefully this can help somebody with good knowledge of the DC universe decide how the fight would go down.