Both top-drawer, but different.
It's like comparing Halle Berry to Charlize Theron. Both are beautiful, but way different. Let's look at the differences between the Python and the Model 27.
First, the Python. The lockwork is an anachronism, using a complex system powered mostly by flat springs, and few gunsmiths really understand it well enough to work on it these days, since it was discontinued.
The cylinder rotates to the right rather than the left, which means that the hand actually pushes the cylinder into the frame, rather than out of it. Also, the hand maintains pressure on the cylinder throughout the firing cycle. You can check this for yourself. With the gun unloaded, pull the trigger all the way through; maintain pressure on the trigger. Then see if you can wiggle the cylinder manually. You can't. It's locked up like a bank vault. Properly fitted, the alignment is well nigh perfect.
The Python was, in its heyday, hand-fitted. In effect, each revolver was given a custom trigger job. The parts operated as smoothly as running your oiled finger over a glass plate.
The Python stacks at the end of the DA trigger pull. This means that if you wish, you can use the DA stack to warn you of the impending release of the hammer, and in effect, letting you squeeze that last fraction of an inch off separately, much like a SA letoff.
The action will demand maintenance after a lot of use; the comment about few gunsmiths being qualified to work on it applies.
Now, the Smith Model 27. I've often called it the "crown jewel" of the S&W lineup. It's finely finished, cosmetically. I love the checkering on the topstrap. The DA action is nothing to write home about, but any good gunsmith can tune it to rival the Python; all it needs is a little careful attention and polishing.
The Smith locks up at three places, rather than the two of the Python. The ejector rod locks into a stud under the barrel. The cylinder rotates to the left; the hand tends to push the cylinder out of its hole in the frame. The action is simpler than that of the Colt, and it's easier to tune. The DA pull does not stack, so the moment of letoff in a DA pull will not be "announced." Some view this as an advantage. More "quick fire" records have been set with the Smith action than the Colt - think Ed McGivern here. Pull the trigger all the way through on a Smith, hold it, and then try to wiggle-rotate the cylinder. Chances are, it will wiggle. Not much, but there will be some slop. The Model 27 is a large frame gun, heavier than the medium-frame Python. It's bulkier, but probably easier to handle in recoil because of its weight.
These are the major differences. Both guns are superb .357 Magnum revolvers. They are just different. I own both and like them both, just like if I were 40 years younger and single, I'd like to date both Halle and Charlize...
John