I own a Uberti 2nd Model and a Colt Signature 3rd Model. I also own two Walkers and two 1860 Armies, and several other c&b revolvers.
Each design has it's own pros and cons; which is 'better' is obviously a personal choice. Here are my impressions:
The Walker is a hand cannon. Big, bold and powerful. It was meant to stop either man or horse, and to do so before they go too close. It speaks with authority and requires that you handle it that way. Heavy, two-fisted and slow, but clearly the boss of the corral.
The Dragoon is strong, still very powerful and somewhat demanding, but more usable. It too is heavy, likes two hands to control, but can be shot well with one hand if necessary; useful up close. Just as devastating as the Walker but more refined; closer to a man's gun than a gentleman's gun. Commands attention.
The 1860 is a companion, a carry gun. It won't reach out a long ways and stop the rider on a horse, but it will own the room. Easy on the hip, easy to the hand, easy on the hand with strength and presence. The kind of gun you'd like to be seen with, and one you'd take when speed and agility were likely to be needed, but not one you'd take to command the field.
As to which Dragoon - much has been made of the differences in the four (the Whitneyville needs to be included) designs, but they're pretty much just 'refinements'. I won't call them cosmetic; it's a bit more than that, but really not worth money or time to consider. Get the 3rd only because it's the 'latest'; get the 2nd or 1st without reservations if they're what''s available. Get a Whitneyville when you've had other Dragoons and want the full experience.
My 2nd Dragoon competes with my Ruger Old Army and my Rogers and Spencer for 'favorite' .44. I like the 1860 a great deal, but it's not the big, powerful voice I expect from that caliber. My 3rd Dragoon is my showpiece, my 'barbeque' gun if you can stand that term. It is the prettiest gun I own and is always looked at with awe by others. Kind of like a piece of fine art.