TMPGEnc has limitations in the if your video is encoded in AC3, you have to extract the .wav file first. Also, I notice that sometimes TMPGEnc and Mainconcept sometimes has video/audio sync problems. As for Procoder, it takes the longest time but the results are excellent (video wise) and I never get a sync problem. (It's the fall-back when TMPGEnc doesn't work.)
I just dump all audio to MP2 with Virtualdub without seeing if TMPG can decode it, it takes about 40 seconds so isn't worth worrying about. So far I have done about 25 - 30 DivX to DVD this way, not had one go out of sync. Procoder is no better in my opinion, I am guessing due to the fact it takes twice as long it encodes 2Pass and 720*480 as standard? You can always set TMPG to that. Plus Procoder costs a fortune to buy, I know people at work with no brains and too much money, I borrowed it, that's how I got to try it. Had to re-install Windows and lost it, haven't felt the need to get it back. For the price of Procoder I could get a Dual Xeon, then I could put all settings to high and still encode faster than Procoder and Mainconcept.