From
http://www.morrisphoto.co.uk
Cokin Z-Pro ND Grad Filter Kit (U960)
This Cokin Z-Pro u960 Filter Kit includes a Cokin Z-Pro filter holder, filter wallet and three graduated filters: Grad Grey ND2 (Z121L), Grad Grey ND4 (Z121M) and Grad Grey ND8 (Z121S).
Cokin Z-Pro Grad ND/Blue/Tobacco Filter Kit (U961)
This Cokin Z-Pro Filter Kit includes a Cokin Z-Pro filter holder, filter wallet and three graduated filters: Grad Grey ND2 (121L), Grad Blue B2 Light (123L), Grad Tobacco T2 Light (125L).
Grad Grey = Neutral Density (ND) i.e. reduces light, does not effect colour. See:
http://en.wikipedia.org/wiki/Neutral_density_filter
The U960 kit is a Grad ND kit, of various densities
The U961 kit is a Grad ND, Grad Blue & Grad Tobacco kit. The ND you know, and the other two are coloured filters (i.e. they will produce a colour cast on your image, for a specific effect). Blue - will make it look cooler. Tobacco - will make it look warmer, etc.
(Google images : Blue Filter & Tobacco Filter for examples)
Neither is better or worse as it depends on what you need.
If you are unsure what to buy - I would recommend the Lee Filter book:
"The Landscape Photographers Guide to using Filters"
