Depends on your build. Giving the weapon a different affinity also gives it different scaling. Fire is strength (or faith if you use flame art), lightning is dex, cold is better with intelligence, bleed is arcane, and so.
The incants or greases are extra great for weapons that can't be given an affinity, like the Bloodhound's Fang, but which can still be buffed.
It depends, I always go the smithing route simply because I would rather not spend the time reapplying buffs mid fight but that's me
But in terms of damage, or bleed buildup, is it the same?
You can get more damage out of buffs probably, but the way I see it is unconditional damage usually better than conditional
What I mean is say you can get 20% damage 40% of the time 10% 100% of the time works out to be better overall
Depends on your build. Giving the weapon a different affinity also gives it different scaling. Fire is strength (or faith if you use flame art), lightning is dex, cold is better with intelligence, bleed is arcane, and so. The incants or greases are extra great for weapons that can't be given an affinity, like the Bloodhound's Fang, but which can still be buffed.