I always thought the reason strip then FUE was better was because with a strip you can take 100% of the grafts in an area after which you can do an FUE to grab hair from areas where you might not do a strip.
So if you have a permanent donor zone of 2 inches high, and you take a 1 inch strip (which you can harvest 100%) and then you do an FUE for the other 1 inch area where you take 50% of the grafts there, you end up having taken 75% of the grafts in that 2 inch high donor zone. Basically the advantage of strip is that it allows you to take 100% of the hair in a given area.
And the advantage of FUE is that you can take hair from just about anywhere including places you might not do a strip from like near the crown or the nape
That's just my assumption though