Just wondering on the quality of ND filters, I'm looking to buy one of ebay for my camera and i've heard good things about B+W filters, but i've seen this Heliopan one and i'm just wondering what makes it $30 more expensive? And is it worth the extra cash??

Cheers

B+W filter
http://www.ebay.com/itm/B-W-ND8-8x-1...item58922a04c1

Heliopan
http://www.ebay.com/itm/Heliopan-46m...#ht_2260wt_922