If the capture resolution and compression are the same, should the pixelization of two captures of the same channel be different with two different programs?

I recently started experimenting with VirtualVCR, after reading some praise about the program in another thread. I don't know if it's just my eyes, but it seems like VirtualVCR captures a smoother picture than iuvcr.

I tried capture resolutions of 720X480 and 640X480, off of cable, compressed with huffyuv.

Is there any truth to this, or have my eyes gone crazy?