Personally I would not buy either. They seem to be ex-office/server computers. I cannot find where it states refurbished. They may well have been extensively used and now coming to the end of their lives.
The second one has a better processor but I see that it does not come with a Vista disc and there isn't any mention of recovery options. It has a smaller hard disc. The first one has a low feedback and the majority are for buyers. no feedback that I can find for selling these pc's.