I start research into a new gun by deciding first what role it will fill in my collection. I started out wanting a plinker, so I researched around and ended up with a Walther P22. It was a great gun, I could shoot it accurately and so fast it sounded like a machine gun until it finally gave up the ghost after 30,000 rounds or so. I basically shot that gun to pieces, even though I maintained it well. I got a Beretta Neos after that but I don't really like it as much- it jams a lot, unless you really crank down on the takedown screw every 20 rounds or so. My new plinker is a Ruger 10/22 with a red-dot sight on it, and it's amazing. I got the Ruger because I've always coveted my dad's. I really like .22s, because they're so cheap to shoot.
For SD, I inherited a former Virginia State Police Ruger Security Six .357, which is a great gun, but a bit heavy and has a fragile (though beautful) finish. I did a ton of research and ended up getting a Glock 19, which I love.
I also bought an early, mint 4" blued Colt Python (circa 1962 I believe) that is just a spectacular gun. My research indicated the early Pythons are perhaps the finest double action revolvers ever made. Mine certainly seems to bear this perception out. I've grouped 6 shots in a 1" circle from a rest at 50 yards. That's 2 MOA from a 4" revolver with factory iron sights! But the Python is too nice and valuable to shoot much, it's a safe queen.