If I were choosing one of these 'scopes I would choose the AOE Maksutov because it is a physically smaller 'scope - both these 'scopes are intended for astronomy and will perform poorly in the terrestrial setting.
Both of these 'scopes have a "longish" focal length and will support magnifications upto about x180 which means the mount and tripod must be quite stable. The "firstscope", being a refractor (longer and more bulky) needs a better mount than the Maksutov and the mounts in both these 'scopes look like they have the same capability. The Mak would be easier to use.
The the long focal length (F# 13) of the Mak' means that it will be a high magnification 'scope with the Firstscope being not far behind. For terrestrial viewing a magnification of about x10 to x30 is a useable range and neither of these 'scopes will do this. Heat haze limits greatly the useable magnifications and the refractor will show a great deal of colour fringing at high mags.
I looked at AOE's web site and noticed that AOE 100mm Mak appears to have a more tobust mount than the 90mm. Perhape you may want to consider the 100mm if the price is right!!
Regards,
Jerry,
