[Wavytone]

From a practical standpoint:

1. Focal ratio. Almost without exception, the commercial SCT's are all F/10. if you are happy with that, fine. If not, look at the commercial maks on the market - they range from f/9 to f/20 depending on manufacturer and aperture. If you include mak-newts, down to f/5.

if you are interested in high magnification for moon and planets, few scopes can beat a good f/15 Mak with a small secondary.

2. Optical quality. SCT's are a bunch of compromises. So are the cheap chinese maks. But then there are Maks from Intes Micro and above all, Questar which optically are about as perfect as theoretically possible. You simply won't get that kind of image from a Celestron or Meade SCT.

In this area you do get what you pay for.

You can get above average optics in a cheap chinese mak, but count yourself lucky if you do because there are some fairly awful ones too.

3. Dew and tube currents.

SCT's have a thin flat corrector with lower thermal inertia, whereas Maks have a steeply curved and thick corrector which takes far longer to cool down. Each poses problems - the SCT will cool down faster but also dews over faster; heating the corrector is a must and on a bad night the dew will win no matter how much juice you pour into the heater.

A large mak corrector is much more resistant to dew - mine usually goes for several hours without heating, but Maks seem to be more prone to tube currents inside the OTA and the way to beat that is to use a tube fan to cool the interior quickly.

4. Size and weight. For a given aperture, Maks are a LOT heavier than the corresponding SCT due to all the extra glass up front, and tend to be longer as well.

5. Aberrations. There are several variants of Maksutov (Gregory, Rumak and others) not to mention the ones with sub-aperture correctors. Similarly there are some variations among SCT's - the bog standard original design, Meade's ACF or the Celestron Edge version.

Among maks, the Gregory design was all-spherical but there are recent designs where the primary mirror is no longer spherical.

The variants have different characteristics and the best one for you depends to some extent on whether you are a visual observer or want to do "imaging" (dreadful word IMHO). For the former, image quality close to the axis is paramount, field curvature is not a big deal. For the latter, image curvature and sharpness well off axis are the priorities and some softness on axis is a necessary compromise - a design optimised for photography is not necessarily diffraction limited on-axis.

6. The back on the OTA and focusser. Some maks have the same back commonly seen on 8" Meade and Celestron SCT's. Some don't - so be careful to check this as the ability to screw things on the back may be quite limited. Some have mirror-shift focussing like the SCT's, some have a fix mirror and a Crayford focusser on the back of the OTA. Again the best choice depends on how you intend to use the scope.