Notice I didn't say best, just the coolest.
1. They are N frames. Sorry fans of M, I, J, K, L etc. but N frames are just cooler than any of the others. I love K frames but the N frames beat them out. Blame Dirty Harry.
2. Caliber. .38/.357 is the premier revolver cartridge. The .357 started us all down the path to high power hand gun rounds. They also served as the standard LE round for many years. They would still be used if you could come up with a 15 round K frame.
3. 27's are available in just about any barrel length you need from 3.5" to 8 3/8"
4"
5"
6"
6.5"
8 3/8"
4. You can also get any of these in nickel if thats what floats your boat.
5. They have great bluing and the triggers are among the best Smith ever produced.
6. Now before you start your counter arguments about why some other model is more cool than the 27, there is one thing the 27 has that no other model does. It has the checkering on the top strap. Sorry the argument ends there
That is my story and I am sticking to it.