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2c on the subject of planets through refractors , from an owner of both a good reflector and an ED refractor who has been observing the planets for over 40 years .
I would recommend also putting a 6" off-axis stop on your 16" to give you effectively an unobstructed `apo' equivalent ( colour free ) to see how well a small aperture works on the planets compared to larger
I do like observing the planets and own an excellent 120mm ED refractor that is well colour corrected, but I wouldn't use it instead of my 14" Newt if the seeing is reasonable and I want to see loads of detail on the planets. 5" or 6" is just not enough light to get high enough magnification to see fine detail. A 6" will show you the red spot on Jupiter but a 12" to 16" will show swirls inside the spot and colour differentiation amongst the features.
There is more to the issue of the appeal of apparently sharper planetary views in refractors ( due to their not resolving the finer turbulence that a larger scope `sees' and marginally better contrast ) . They are not good at showing complex smaller scale and larger scale band detail due to inability to supply colour differentiation of features in the disc view.
The ability to show colour differentiation needs a larger exit pupil and this is where the extra aperture comes in. If you are using ( maximum ) 2mm pupil for this ability on a 6" you only have 75X ( too low mag for resolving detail ) but on a 16" it is 200X which is at the lower end of useful magnification for planetary observing . A 1mm pupil will be too small to show clear colour differentiation with any size scope - but it is more likely going to be needed with a refractor to get the magnification high enough ( ie 150X on a 6" refracator) .
Even when the seeing is not so good colour differentiation will show you a mass of features that are invisible in a smaller aperture which is operating at a small pupil showing essentially only shades of grey on the disc features and that is even on nights where the seeing is soft - the small telescope will show a soft disc with mimimal detail but the larger scope operating at a larger pupil ( which activates the cones in the eye ) may show a wealth of detail ( albeit soft ) due to colour differentiation of the features .
I hope I explained this point clearly enough .
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