Didn't you check the hints given in the introduction to this forum http://moodle.org/mod/forum/view.php?id=596 ? This is a common question, you can find similar discussions through "'Using Moodle' advanced search facility" mentioned there.
Back to your question: Both machines are over kill at first glance, if you have 300 students enrolled and just starting Moodle.
Unless all 300 have to go through an online test at the same time and/or most of the usage is in campus, which is a contradiction anyway, I would go for an external hosting. Due to the large numbers a machine at a professional hosting service costs less than buying and maintaining a single server. And big hosters have tools you can access 24 h in case something breaks down. Just two days ago I witnessed an online test cancelled because the "IT" was not available during the weekend.
From the numbers you mention, you can even start with a VPS and shift to a dedicated server if the need arises.