First up I think it really depends on one level as to whether your a Douglas fan or a Lockheed fan because in terms of quality they are equal as the others have outlined, one has Accusim one does not both have FE assistance, maintenance control or management etc., but the Constellation is probably more immersive.
I have both but I like them both for different reasons. The L049 by A2A will not replace the Jahn L104G/H (and those ones by the way are also excellent as far as accuracy and modelling is concerned they just do not have modern VC's with all the textural bells and whistles. As for the DC-6 my personal view is that it is not as difficult as the Connie to operate and fly. But both require you to actually spend time learning about the aeroplane, its performance, how the systems work etc.
As a tip, which ever you decide upon and get, whenever I get a new aircraft I put myself through a type rating program for it, that is I spend a lot of time reading the manuals. Then I will get used to the VC with the manual handy then move up to engine starting, taxying and general grand handling before even attempting to go flying. The I will do some take-offs, upper air work (Stalls, turns, climbs and descents) before I move onto to doing circuits and touch and goes. After that I move onto to instrument work and begin flying approaches, NDB, VOR and ILS. Finally I finish off with some emergencies, shutting and engine down etc. Basically all up between 7 to 15 hours of sim time before I start flying anywhere else. I also base myself at the same airport so I am familiar with the terrain, radios, navaids etc. I find this will also sort out any bugs, quirks or other issues with the model in the sim or my understanding of it, because I have found like all things, the better I know the bird the more I can enjoy it (and sometimes hate it too).
All in all I am a round engine nut so I like em all. Flown enough turbines for real to appreciate glass cockpits etc and unlike a lot of simmers I grew up flying aircraft with steam driven gauges and primitive navaids and complex electrical and hydraulic systems to not be daunted by them.