I'm 6'2" and have the regular length Burrow and Incubator. Your concerns were the same as mine when I was trying to decide. I went with the regular length and have never regretted it.
My Burrow has no overstuff and it has done me well. My Incubator didn't have any either, but as I camped into the low 20s, I found my personal comfort to be about 25-28* for the 20* rating. I eventually ripped a seam and added about 1.5 oz of "overstuff." Took it to 20* with no issues back in February. With no overstuff, I would get migrating cool spots thru the night as the down would shift slightly when I rolled over. With overstuff, there is no room for migration.
The newer UQ suspension he uses now helps a lot with CBS. I redid mine old version with great results.
So, IMHO, Burrow -- no overstuff. Incubator -- 1-2 oz if you sleep cold.