In my Paintball Store, we don't have any trouble selling most any marker. For my money, our rental fleet is all Tippmann. Out of 60 markers we have trouble with only about 3 or so per match, mainly due to broken paint lodged in the bolt. We used to run "other" types but got sick of the delay, and mad players during the match. I'm the Airtech also, and it was trouble to have at least 20 markers and players in line waiting. Just my two cents.
In-line markers are more reliable than stacked in my experience of 10yrs in the retail paintball business.