the reason base update should go first, is that sector updates always add new and more exciting content on the short run, but every sector update (unless it's something very well minded and not just adding level cap and armors) ends up being boring because people completed its challenges (just think about level cap in ob and now).
instead a decent base update could bring some fresh gameplay, and since nobody play base, it would last longer because base itself would be a new mode. less important, what serious and caring gaming company would leave his game half completed?
by the looks of it the sector update is well minded and can bring lots of new stuff, but since base has been ignored all this time, and sector would be still updated base would be the best option