I personally think the new series is better than the old one, i havents een any of the OVA for the old one but i did see the whole series of the old one and am current on the 2005 series: currently 32.
The new series goes much more into things and seems like its gonna go all the way to when who will do the kurenai tenyou is decided and we might actually get to find out what kind of play it is =P
It seems that on episode 24 or 25 of the 2005 series is where the old series ended. and the new series is countinuing.
It is definitely a different series, some stuff they changed I dont like and other stuff I do but all in all I would say i like it better, the widescreen/higher quality animation is a + too but i dont really care all that much about animation. Though it would have been nice if the old episodes I had were actually high quality not like 80 MB avi files.