I like the 357 Sig but it is expensive and loud as hell. You can use the same mags for 40 S&W although it may need a different follower. Not sure about all manufacturers mags.
Most well made guns are about the same for reliability. Sig, Glock, HK, CZ, most 1911s, etc are all the same reliability wise and none stand out good or bad. They are all good, but all can malfunction.
Many guns available in 40 have a factory or aftermarket bbl in 357 sig. You have to decide what features you like and go from there.
Steel vs Poly,
Hammer vs Striker
Single action w/ a safety or a Double action first shot with a decocker or one in the middle like a glock or xd.
9mm, 40, 45, 357 mag or sig are all about the same stopping power wise with modern defense loads against people. Big dangerous animals are a different story. Where and how many times you hit are more important than what you hit them with so I would go with something you can find ammo for and afford to practice regularly.
I doubt the 357 sig will ever get to the popularity of 9mm, 40 or 45. It's one shot stopping power is marginally better, a small margin than 9mm but costs much more to shoot and harder to find ammo.
Also, that is a moot point because anything worth shooting once is worth shooting until it stops moving.
But it is loud, can have an impressive muzzle flash, can be switched over to a more common cartridge with a bbl change and is unusual enough to be cool.