Unsure which resolution you should pick? Please download a few scans and compare yourself.
9 Mega Pixel / 3000 DPI Film Scan:

18 Mega Pixel / 4000 DPI Film Scan:

Because 4000 DPI, TIFF slide scans are 100 MB or more, they can be downloaded per request.
One more thing... Just because you will get high resolution negatives scans, does not mean they will be quality. Resolution is just bits and bytes, it is how many pixels my scanners pickup-- not quality. To get a negative scan that looks better than your original, you need to do some editing. And pressing the Digital Ice button will not help. Find out how we will edit your negative scans, here.