Back to the topic of regrets... I ordered a five seater and regretted it after 10-seconds. There was more to it than just the seats... but it was a factor.
As a photographer/video guy, I have totally filled my Model S. So, I fully intended to order a 5-seat Model X when I traded in a month ago.
They had a 6-seat inventory vehicle that offered an interesting alternative. It had an $11,000 (Canadian) discount, autopilot-1, premium sound, winter package and blue paint.
So at the same price, I could order a basic 5 seater with no features, or the fancier six seat.
I was responsible and ordered the 5-seater with my sales guy in the dealership. I regretted it as soon as we clicked 'enter' and immediately asked him to cancel it.
The sIx seat is definitely less practical for gear. I'll be playing Tetris around those big, unmoveable, non-folding middle row seats for years, but it was more important to have a car I enjoyed on a purely personal level when I wasn't carrying stuff.
Admittedly, my situation was different because it wasn't Apples-to-Apples. If I ordered from scratch, I would certainly pick the cheaper 5-seat. But I can say now, I do enjoy looking in the rear view and seeing that sexy six seat interior over a typical bench seat.