Nick,
I'd just ask who are you collecting for?
If it's for you then it only matters what you think.
I collect for me and although I DJ I don't buy anything on that basis. I buy what I like and what I can afford on original labels. I have the complete run of Grapevine Demos but wouldn't play them out for the reason Pete keeps his 'northern led demand' releases seperate from his 'released at the time' British.
Whatever you decide to do, do it for you nobody else, is the best advice me or anyone else can give.
Ged