In theory a lab scan should be better, right? They've got the expensive equipment and trained personnel. But in reality, that equipment might be poorly maintained (and getting elderly, since it's probably 20+ years old at this point), and that staff might not be trained well, or might not care about your pictures all that much.
I started DSLR scanning this year, and I'm really happy with the results. Prior to that, I'd sent rolls to a few different labs online. My best results so far were from Memphis Film Lab, and I would definitely recommend his service, but I didn't care for his color corrections. That's fine, he has an ordering option to not make any corrections, but in order to have leeway to make your own corrections, you may want to pay extra for the 16-bit TIFF scans and deal with 140-MB files. I can DSLR scan, get 20-MB 14-bit compressed RAW files and tweak the colors to my heart's content. I don't have quite as much resolution as Mr. Memphis' scans, but it's more than enough.