Tool preference

I think you got confused about the functionality of these tools. To put it short: Gordian Knot is an integrated frontend tool for the entire process of encoding, while VirtualDubMod is a video editing software based on Avery Lee's VirtualDub. The -actual- encoding is done by VirtualDubMod and it comes bundled with Gordian Knot.

Yes I know that VDubmod is used in GKnot during the encoding. But is the compressibility check just as useful than if you used VDub on its own to encode? Using VDub by itself there is no method of matching the quality of the input file, it's pure guesswork to end up with 100% quality.

Well you can do a comp test manually single pass @quant=2 SelectRangeEvery(280,14) # that's for 5% SelectRangeEvery(700,14) # 2% After that, you'll have to crop, resize and create an avisynth script yourself, as well as calculating the bitrate with a bitrate calculator. Or you can use GK as most people do, to let it do all this, then feed the avs, edited or not, to vdubmod. All in all, it's the same, in the end, it's vdubmod anyway. It depends how hard you want to make it on yourself ;)