My local preschool is looking to buy an interactive whiteboard and as a member of the management committee I will be part of the decision making process, but I have little experience of them. Does anyone have any recommendations/preference/advice?

It seems the choice is between SMART and Promethean. I've Googled for SMART vs. Promethean but apart from marketing material for each I can't find any good comparisons.

Any advice gratefully received