The bigger the better to some extent... There are rubbishy ones that are cheap but NOT WORTH IT. There are probably a number of makers (Manfrotto, Slik, Gitzo) that make suitable ones.
But you might consider:
1. the limit of weight tolerance, with enough stability and HEIGHT. I have used a relatively light and compact tripod (Manfrotto 190) with Blads. It is possible, but the lower limit, IMO.
And I might brace the whole thing with weight (this works with care) and only carry it when I am making a compromise. I have found as much limitation in the legs not having enough length in steep terrain.
A bigger tripod might be pretty manageable for a 'few miles', although reducing weight is always nice. Carbon ones might be a help, but are expensive.
2. look for replaceability of all components...the tripod might end up like grandad's axe, but should last for a LONG time even if bits are replaced.
3. has a good tight locking head. In my humble experience, this is often the bit that rocks.
4. it is OT, but consider a back pack...I have found this the single most benefical ergonomic step in carting gear for landscape.