Great questions. My untrained opinion is that beef has flavor profile or taste that is different compared to pork. That said, the simple answer theoretically, is there should be a best rub for beef and a best rub for pork. I may be wrong but that is what I surmise.
That having been said, with my limited experience, I attempt to make the best rubs I can. Guess what, I use them on both beef and pork.
Think about wine, white for chicken or fish and red for beef. That theory was dispelled ages ago.
As for sugar in a rub, my opinion is that it is often over used just like salt.