Grease or wad, both are there to do the same thing, keep the fouling soft,
Which is best from a shooting point of view, which ever one works best in your gun, the difference is marginal at best.

Pro and cons
Wads are more expensive to use but are much cleaner as far as your hands are concerned.some of the lubricants used in the wads are better at keeping the fouling down for more shots than lard or Vaseline

Grease is cheap to use but your gun and your hands soon get a good coat of sooty grease.You can buy the same lubricants that they put in the wads but this pushes the price per shot up or you can make your own mixture.

Personally i use wonder lube 1000 in wads when shooting BP revolvers and the same lube on the bullet when shooting BP rifle, i have found it keeps the fouling in check for the mornings shoot and makes it easy to clean up afterwards.

No doubt someone will have a different opinion

Regards
Clinton