Bleu for me!
Bleu is a bit more conveniently placed for access to main areas of track/grandstands. I have never camped at Beausejour, but its quite close to the Porsche Curves viewing areas I think.
Dont need bikes particularly for Bleu, tho they can be handy anway for getting to supermarket and out to other parts of circuit when the (car) traffic is busy. I reckon you would certainly benefit from bikes at Beausejour.
I like Bleu best, but thats just personal - some of the regulars here camp on Beausejour and can probably let you know more about it. I think space is easier on Beausejour if you are arriving on Thursday, certainly Bleu was pretty full by Thursday morning this year.
These are the two easier campsite to get tickets for, but dont leave it too long before booking if you want to be sure. Dont buy through ticket agencies either, thats an expensive rookie mistake!
I am sure others will add to this but hope you have a great time for your first visit wherever you end up.
Fran