I'll keep it short, I got a baby crying. Root, hot, and fill passes are generally done down hill with 5p. Your Low hydrogen, (7018), cap should always be uphill. The gurus on this site will fill you in on why and how. Baby needs a bottle. . . . .
Generally I would say vertical up is preferred over down for most applications by alot of people. Certainly deep penetrating (F3 group) stick electrodes are reasonably foregiving and capable of excellent welds with a downward progression. And a really good welder can probably weld about any process and electrode downward successfully if they are well skilled and really determined to do so. And downhill is an excellent way to overcome burn-through problems on thin material. However I am generally skeptical of downhill welds. Few welders have done enough destructive testing of their own work, on various metal thicknesses and joint types, to know for sure if they are getting reliable fusion and internally cleans welds downhill with short-circuit MIG, 7018, E71T-1, etc. Due to the faster travel speeds necessary, lack of fusion, porosity, and inclusions are considerably more likely than if done uphill.