The dealer you buy from can ease the pain a little if you have a problem with the unit, acting as a liason between you and the manufacturer.
Lot's of mergers so to some extent, they are all a crap shoot. FLIR & Armasight, IR Defense & Trijicon. Pulsar has generally had good customer service.
If the $$ is similar, I'd go with a company with a well-established history to go on. I own or have owned ATN, Sightmark, Pulsar, and FLIR. If I were in the market today, I would go Trijicon.-JMO