In theory scratches are at least 50% more likely on bulk loaded film,
due to an additional pass through the light baffle on the cartridge lip during loading,
and the greater likelihood of grit or debris on the felt of a reused cartridge.
Avoid trouble by using better quality reloadable cartridges and examine them before each reuse.
In the past I bulk loaded my own film but haven't done so in years, as I now use much less film.
But I will keep my bulk loader, in case those little yellow and green boxes ever disappear from store shelves...
Chris