Hello CinkBeast and welcome to cloudy nights.
I do not have a celestron astromaster 90, but my thoughts based upon other scope I have had is as follow.
Long refractor, limited chromatic aberration, easy on eyepieces, no need for optical adjustment (collimation)
Probably the mount is shaky, There is some chromatic aberration, (CA) probably enough to degrade Jupiter, Mars.
Only 90mm of aperture. For dimmer targets, it does not have enough aperture to pull them, out of
light pollution. If you will be primarily observing from a dark place then no problem. EQ mounts are not
as intuitive to point in the sky for a beginner. (altitude-azimuth) Alt-Az is easier.
These are all variants of a dob. In general what the dob buys you is.
Most aperture per dollar.
Super stable mount no shakes.
You can make a home made push to system to find faint targets in light pollution.
Reflector so no CA
You will have to collimate them from time to time for highest performance
Orion 4.5 inch dob. Smallest non table top dob. An adult will have to put it on a small table, or
some bricks etc to bring the eyepiece up to a comfortable viewing height. Can be carried with
one hand. Long tube, easy to collimate and easy on eyepieces.
6 inch dob. A much more capable scope. Bigger and heavier but no harder to set up.
If stored in a warm house and taken outside on a cold day, you will have to wait about 30 minutes.
for it to cool down. Once again easy on eyepieces, and collimation.
Table top dob. Zhummel 130 or AWB one sky.
Super small and portable. Wide field of view which helps to find object easier than a longer scope.
You will have to collimate this often, and wide views will require better eyepieces.
Hope this helps.
Edited by vtornado, 16 January 2020 - 04:47 PM.