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The point about Saturn looking better then Jove is a good one - I think even showing someone Saturn with an 80mm refractor who has not seen Saturn before and seeing the rings etc always creates an impression.
Jupiter will always be a tougher object - have you tried using some colour filters? Also remember, that for several years to come, Jove will be low for us and Saturn will be high.
My view is that you will nearly always get sharper views in a Newtonian vs an SCT. I don't however know about the optical quality of your SCT.
The issue you will also have with a Dob especially something as large as a 16" or 20" is tracking. At high magnifications, no matter how great the view, it will get annoying after a while trying to track at high magnifications - gather you have observed through large Dob's? Perhaps an equatorial platform is the way to also go for you.
Down the track are you also interested in doing some planetary astrophotography?
So to answer your question, optically speaking, a well made Newtonian mirror should give you way better views in my mind vs an SCT. But Jove will be a tougher object as it will be low down.
My money would go towards a slightly smaller Newtonian (say 12" to 14") with maybe a new EQ8 type mount, or if you want to go Dobsonian, then build in the cost of an equatorial platform.
But, if you simply want more light gathering power to also do deep sky stuff that doubles up as a better visual scope for planets, then a 16" to 20" Dob with a well made mirror and good tracking will satisfy you - not sure about the optical quality of some of the Chinese mirrors - also consider that cooling ect will come into play more and more with an increase in aperture - many years ago when I had my 10" Dob with a well made Parks mirror, I remember being at the ASV's Parer St observatory in Melbourne and comparing the view with the society's 20" fork mounted reflector which had been heating up all day in the observatory - the 10" won hands down! It was a sharp reminder on the other things that come into play with larger telescopes - more complexities to deal with - so larger is not necessarily better.
Good luck with your decision.
John K.
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