It probably comes with TE3, but if necessary then "sidegrading" from TE4 to TE3 is
a simple process best done before you have any content on the disk. I haven't seen complaints about refurbished TiVo hardware, but anyway it will come with a good warranty and Weaknees is a great company.
In my opinion the Roamio Pro is the last great DVR that TiVo may ever produce. Since you don't specifically need the added A/V features or faster streaming capabilities of the Edge, there's really is no reason to spend that much more money just to work through all the bugs in such a new product, not to mention the bugs and unfinished features that may never change in TE4 which is what you'd be stuck with on an Edge.
I just replaced the hard disk in our five year-old Roamio Pro to give it a new lease on life rather than upgrade, and I have already decided that if and when the whole unit goes then we're moving on to Channels DVR.