Well, to summarize this as the creator says:
TDC starts at the beginning of the DOS era, exodos at the end, which is why exodos is much bigger, because of much bigger games.
The aim of TDC is to preserve every single game and some time it may get even bigger than exodos. The creator says, this will already happen with the next release as he is integrating all games from exodos.
As TDC is released every six months I hope we will get this soon