Attached below are results from more comprehensive & comparative tests.
(Left image is Meade, right is ø42mm 180 mm FL doublet (from Russian binos).
Meade has big problem with field flatness at corners of APS sensor, while doublet behaves better.. This is not a big problem because of heavy vignetting at those distances from frame centre... and cropping helps a lot.
However, Meade is quite flat in the central part (inside distances 1/2 of the shorter side of the frame), while doublet has a bit of coma, visible closer to the centre of the frame (where Meade is OK).
Also, I noticed a slight CA with Meade (easily removable with PtLens), and no CA with doublet (I was expecting the other way around)..
All in all, doublet is definitely worth the money I paid for it
.