I have only ever used VDR in Australia. Its good and the primary advantage is that it is well integrated into the LMCE interface so you don't feel like you are going to a different application just for TV. VDR is designed with DVB exclusively in mind, Myth was not. The devs are German (I believe) so they have a vested interest in DVB, whereas the Myth devs are N.A. (I believe) so they do not. VDR is definitely the future for LMCE (etc) outside N.A. (and a handful of locations in S.A. and Japan, etc) as the vast majority of the world uses or subscribes to the DVB standards.
Having said that, the VDR implementation in LMCE is very young (mostly CHT's work). Although VDR is a client/server architecture, in LMCE it isn't yet implemented that way so you can only watch TV on the device with the card in it (without a hack). The VDR integration into the Orbiter, VDR's OSD and remote control functionality is still very patchy. And there are some rare stability issues where VDR crashes out (or rather its wrapper) and you need to hit TV again....
Most if not all of this is being worked on right now, and the hints I have read are that most have been resolved and will be pushed out in an update "soon". Soon in this community is a very relative term! But I got intimations of weeks rather than months, so I have no intentions of ever going to Myth, I would rather wait.
Do a search for Totallymaxed comments with VDR in the criteria field - he has made several comments about the progress in recent weeks (he is CHT).