From my understanding, both PLA and ABS can be treated with acetone to make them smoother. So when they are treated with acetone, which is smother PLA or ABS or are they about the same?
When I search online, all I find is how to treat the objects.
ABS filaments will smooth well with using acetone, it's been used for a while now.
For PLA filaments it's a different story, pure PLA will not smooth out in acetone and it will likely only cause structural failure of the product.
However most PLA filaments aren't pure PLA, they contain additives including ABS that react differently when exposed to acetone and the reaction will really depend on the manufacturer of the filament, only a few PLA filaments are known to smooth like ABS when in an acetone vapor bath, it is the case for ColorFabb PLA filaments and it is absolutely not the case for bq PLA filaments that only soften and break when exposed to acetone.
You'll have to make small tests with different brands of filament to see which smooth well and which don't but if you want to go fast either go with ABS or use other smoothing techniques such as sanding + 3D print Smooth On epoxy.