I ran a little experiment with regards to the frame count mismatching and here is what I got

PgcDemux read the NTSC GOUT DVD of Star Wars as 174262 frames
DGIndex read the m2v file PgcDemux created as 174261 frames
VirtualDub via AviSynth read the d2v file DGIndex created as 174258 frames

PgcDemux read the NTSC GOUT DVD of The Empire Strikes Back as 179669 frames
DGIndex read the m2v file PgcDemux created as 179671 frames
VirtualDub via AviSynth read the d2v file DGIndex created as 179668 frames

PgcDemux read the PAL GOUT DVD of Return of the Jedi as 189451 frames
DGIndex read the m2v file PgcDemux created as 189451 frames
I have yet to open the d2v file DGIndex created using VirtualDub / AviSynth.

Is the small variation in frame count normal when working with NTSC material or have I missed something?

My settings for PgcDemux are:

Input IFO: VTS_03_0.IFO from NTSC GOUT DVD Rip
Mode - by PGC
Options - Demux video stream CHECKED
Demux audio streams CHECKED
Demux subpic streams CHECKED
Create CellTimes.txt CHECKED
Include end time UNCHECKED
Create Logfile UNCHECKED
Create a PGC VOB UNCHECKED
PGC Selection: Titles
PGC # 01 --> 02:01:00:22 SELECTED

In DGIndex the only setting I have changed from the default is:

Video -> Field Operation -> Forced Film CHECKED (For the two NTSC DVDs)

In VirtualDub the only settings I have changed from the default is:

Video -> Fast Recompress CHECKED
Video -> Compression -> Huffyuv