Here the business case is where to save the most money:
A. - Spending a lot of time once to deploy not so many (as you always buy the cheapest, with al respect)
B - Spend some more money in an investment of a brand/type with long lifecycle
Pro for A - lower investment on hardware
Con for A - high cost on hours to run/maintain for IT (engineers, Helpdesk) and end-users
Pro's for B - run/maintain costs are a lot lower. Not only for deployment, but also (or especially) for helpdesk. As most of the machines are alike, one can rule out HW/driver failures a whole lot faster.
Con for A - higher investment on hardware divided over three/five years
I would now where to put my two cents...