Spool valve markers are
generally higher maintenance than poppet valve guns. Most of them have to be well lubed before every day's play and they can be a lil more unpredictable. On the other hand the Ego/ETEK range are pretty much bullet-proof reliable, just chuck em in your bag and they'll work next time you get it out. Maintenance is required infrequently and when it is, it's very simple, fast and well documented in the manuals
available here.
I wouldn't recommend getting an ego8 or older due to a few slightly more fiddly reliability concerns (QEVs) so get the latest/prettiest you can afford.