sat tuners from 1 - 4 as i found 1 not enough if wanting to record and using multi sat dishes.Newer boxes can have removable tuners to switch from sat to cable/terrestrial.
excellent picture quality which newer boxes are getting.
support is vital with many open sourced backers.
internal hdd is a must as using 2tb in some boxes,not able to afford 4tb yet.
old sat box with 1 usb was very limited.
boxes now come with 2 or more usb slots as i used a usb stick for epg storage.
box needs to be fast and not hang with too many extras loaded.
Unsure whether different boxes have a higher output from usb ports with issues with passport hdds,i suggest powered externally.
hdmi input for running something like a bluray/android/other through box only seen on my et10000.
spdif if wanting to hook up to sound system.
only used lan cables for boxes but some have built in wifi or if not one reason why box needs extra usb ports so one can use a wifi dongle.
good remote that does not feel cheap and works without having to aim straight at box.