Given interlaced source, what advantage does KVCDX3 have over KDVD? The resolution is oddball and both support MPEG-2. Did it start as an experiment to try to increase detail?

Secondly, why use SKVCD NTSCFilm instead of KDVD? Is SKVCD, essentially, the same as KDVD but at film fps with the pulldown header trick for NTSC hardware playback?

(Question isn't about MPEG1 which I think is useless for high-motion source. Unless it's film or quite old, I prefer NOT to deinterlace because it can create problems and takes longer to pre-process.)

720x480 is 345600 pixels. 528x480 is 253440. Far less pixels to encode, and barely any quality difference viewed on a regular TV ( 720x480 is just a little better on a HDTV ).
So we can get a higher CQ value to encode. It's really the best compromise between quality/resolution. You can always encode KVCDx3 as MPEG-2 interlaced, and burn it as SVCD, if your player supports it. They are basically the same , but SKVCD was done as a substitute for SVCDs. You can really get far more time on a CD at 352x480, and also 352x480 is Half D-1, which is a standard DVD resolution. 480x480 is not. So people that want to move their encodes to DVD in the future, they only need to re-encode audio if it was done a 44.1Khz. Also the bitrates on SKVCD are set way lower that KDVD values. True, but most of us usually encode just that, Film .

-kwag

When I use TMPGEnc Author, it will not accept 352x480 for 16:9, so is Half D1 confined to 4:3 for standard DVD resolution?

Yes it is. Half D-1 can only be 4:3. Full D-1 can be 4:3 or 16:9.
http://www.dvddemystified.com/dvdfaq.html

-kwag

Thanks. 16:9 KDVD 352x480 half D-1 output muxed as DVD with BBMPEG and burned as SVCD does play well on both my APEX and Cyberhome machines. In fact, it appears to be a very compatible format.