Can anybody tell me if there is alot of difference between and 87L board and a 95L.

About eight litres. That is a fair bit if you had to drink it in beer.

Anyway they say width is more important than volume.

I knew that was comming lol. Just dont know weather its worth buying the 95L

If you really want a sensible answer, you need to supply more info.
We have a soothsayer on the forum, but I'm not too sure how good he is at mind reading!

What type of board?
What's the widths, of the boards?
What conditions do you want the board for?
what's your weight?
what's your experience level?
What sails are you using with it?

IF you dont know which you should get then you probably should get either and get a bigger board