I know there has been a big discussion from time to time over the bitrate in convertxdvd and the project settings sp,mp ect ect, so please dont hate me for bringing this question

Just to clarify I usually put 2 movies on a standard dvdr 4.5gb and I have always use the Automatic setting and let CXD decide whats best.
Now my old tv was a hd ready 26" so I used to watch all my coverted dvds via dvd player on it and they looked fine and I was very happy with them. I have since had to upgrade my tv as it broke so now I have a 32" full HD tv and ;lay my dvds via a sony bluray player. My commercial dvds look fantastic when up scaled and I'm very happy with them but my dvd-r's look really bad (pixelated) at the scenes with lower bit-rate (darker scenes). I know that CXD uses VBR and in less complex scenes it reduces bit rate and ups it in more complex scenes so I think this could be my issue.
So My question is , is this because of the lower bit-rate that they look bad and pixelated? and also Can i improve on this in future conversions by changing the project setting from Automatic to SP and using dual layer 8.5GB discs instead of the 4,7GBs?
(P.s I know that HD in a newer tech and looks Superior ect but at the moment I'm happy with DVD for various reasons and if I can get my conversions looking like my commercial Discs do on my 1080P TV I would be happy.)
any help/advice would be great.
Thanks