Aren't the biggest factors here the budget and how many computers you need/can fit in?
It's 'only' a student lab. Spend the bucks on a decent server box. the next big thing might be the service contract you'll get with what option.
Who signs the check for all this? What is the lab for? If it's experimenting with hardware, don't spend too much on it.
Can you give some more information on this project?