lightweight disc or frame?

ozzzyosborn206

Hi all this time or year i always get bored with a lack of racing and spend ages looking at various things to buy on the internet, I currently have a servile p3 TT bike with a ffwd disc, quite a few people recently have bought new TT bikes, Shiv, Plasma, P5 etc. Does anyone know what sort of gains could be had from upgrading to one of these frames(probably a new Plasma or ridley dean fast as can get a good deal from LBS on them) compared to a lightweight disc? I knew a few people who have recently got them and they say they are incredible but then would anyone really admit they aren't worth it after shelling out that kind of money for one?