What Festool calls a DC, I call a vac ;D. A vac is designed to work at the static pressures that work well with small tools with small openings. A large full shop type DC is better for larger ports in bigger tools. So, yes a vac is generally better than a DC. But, some DCs might work OK. I do have my 2HP commercial Oneida attached to some benchtop tools with 2.5" openings and it works great. Since I have a nice vac, I haven't had a reason to try it with the smaller openings on Festools. The vac is more convenient since my cutting and sanding worksurfaces are in the middle of the shop and my DC plumbing is along the walls. The vac is also quieter, much nicer for extended sanding sessions. My DC is in a closet, but just the air rushing through the piping is louder than my vac.