The ETX80 is a short focus refractor [giant monocular] ok for wideangle views of nightsky or daytime landscape.
The ETX-90 [and larger apertures] are superior Maksutov optics but slower f/10 ideal for planetary/ lunar viewing but pretty good for the brighter deepsky objects too.
Both scopes on the same type of mount but with the longer focal length Maks the set-up before a session is more critical.
I have a ETX-70 refractor and love it and it makes a perfect astrograph and even from my suburban home it outperforms big Dobs from dark locations. My hompage at
Meade ETX-70AT
This page also links to my Meade DS2090 and Meade LX200 recent imaging etc.
Nytecam