I checked your Studio DV25 sample and the HuffYUV sample, and HuffYUV is the clear winner regarding quality. The other formats are not competetive for analog captures IMO...
One thing I noticed is that the Studio sample is BFF (and it is also flagged correctly), but the HuffYUV sample is clearly TFF. This will matter if you want to deinterlace it later.
Maybe check the settings for the HuffYUV codec. For NTSC the field threshold must be 240. Also be careful to use a version which has patched out some bugs, this would be version 2.1.1 - CCESP Patch v0.2.2.
Also your HuffYUV sample does have a PCM audio track, but it is completely silent. You need to check your VDub settings for audio,,,
Using VirtualDub for capturing is one thing I have always recommended. For my hardware it is absolutely essential, because my capture card does not handle audio. Audio is treated by my sound card, and since video and audio run on separate clocks, sync problems are guaranteed unless I use VDub. VDub is the champion when it comes to deliver captures with perfect video/audio sync.
Cheers
manolito