Are you buying to shoot or collect? If it's a shooter, go buy the 27. As a collector's piece the Python probably is a better buy.
I own a 27-3 with a four inch barrel and it's one of my favorites. I love the balance of the gun and it is accurate as any gun I own. It also handles heavy magnum loads with aplomb. Obviously, it is no safe queen. I'm confident that if it ever needs service I can send it to Smith and have it repaired as good as new.
I've had the opportunity to fire a Python. I was a little disappointed with the way it handled, to be honest. In my opinion, the Python double action trigger is not as good as a Smith. It certainly is different, with this weird stacking (increase in resistance) at the end of the pull. I very much prefer the Smith trigger but, I suppose, it's all a matter of taste.
If you're buying to shoot it, keep in mind that the gun hasn't been made in several years, and that means parts and knowledgeable gunsmiths are a diminishing quantity.
Now, as a collector, I've noticed that Pythons command significantly higher prices than 27s. My guess is that they'll continue to do so and will appreciate at a faster pace than 27s over time.
So, it's a question of choice. Do you want a shooter or a safe queen?