I have three 4" 66 (no dash) revolvers. One is a Pawn Shop reclamation. It was mechanically tight, but the previous owner had not taken care of the finish or stocks. The price was right, so I bought it.
A gunsmith friend of mine did a trigger job on the gun and a light glass beading to remove the bad scratches. A new Hogue grip, and the gun looks and shoots like new. Total investment is about $600 which means this gun will probably never leave.
From an investment angle, the gun is not worth much. From a performance and fun angle, it is priceless.
I also have one 6" Model 19 which is also fun to shoot.
Here are my complaints with both guns.
While the blued Model 19 is pretty, it is hard to keep shiny. Finger prints and oil smears show very clearly.
The 66s are easier to keep looking nice, but it is very hard to get the powder residue off of the front of the cylinder after you shoot the gun. I use a soft toothbrush and Flitz to handle this issue.
As far as which one to buy, I would say both.