You asked for as unbiased opinion{s} as possible... Well, it depends on what you want to do with the car; if you are wanting to go street racing, getting that coil spring rear to hook up is difficult. If you just want a cruiser, then they are wonderful. Bodystyle is subjective as is colour. [ I think the 72 is the cleanest of that series myself...] Also, are you staying 100% 'original' or are modifications in your future?
Lets face it - and I will undoubtedly be excoriated severely here - but the build quality and ride is superior to our Plymouths. Not as good as Olds for example, but better than Mopar. When I say 'better' , I mean lower NVH, more damping and generally better materials. The [power] steering is more direct.
If you dont mind mods, power [and handling] are much easier and less expensive to make than your Plymouth. Parts are easier to source, etc.
BUT!!!! One must be VERY careful to not get 'taken' when buying one - SS cars are relatively easy to clone in the 68-72 years, and the prices are off the charts worse for real and rare/high horsepower cars. Of course, thats true for Plymouths too....

Anyway, my opinion is that if you want one, get it! You will find it to be an enjoyable car to drive and easy to work on should the need arise. They dont rust any worse than other cars of the era, and not as bad as some. Real SS cars especially have usually lived a hard life, but by now have probably been restored and should be good. Of course, that is VERY dependent upon quality of restoration...because of the ease of working on them and the plethora of parts available, there are LOTS of very poorly done examples out there. caveat emptor.
Basically, they are neat old cars that held their own back in the day; the super fast guys usually had a Plymouth or a 55 Chevy, but any big block Chevelle will certainly keep up with traffic and be a joy to bury the loud pedal with occasionally.
best of luck in your search.