Since I bought my Ruger SP101 last year, it has been my everyday carry piece, almost exclusively. There are a number of reasons why, and I'll get to that, but there are also a number of myths about revolvers that "trick" people into carrying them with blind faith.
The biggest myth surrounding revolvers is that they "can't jam". I beg to differ. Not only can they jam, when they do, it is FAR more serious than when a bottom-feeder jams. It takes only a minimal obstruction to lock up a revolver's cylinder. The most common culprit on the range is a loose primer pocket that lets the primer back out slightly and binds the cylinder. The most common culprit on the street is loose change surrounding an improperly pocket-carried J-frame.
Full-moon clips can warp and refuse to enter or exit the cylinder as well. Then there is what happened to me today. Apparently HS6 is the dirtiest propellant known to man, and after only 25 rounds, the front and rear of the cylinder were so caked with carbon that it would not close. I wiped the cylinder with my shirt and all was well once again.
Anyone who says revolvers "never jam" is an idiot. However, immediate action is a little easier . If a round doesn't fire, just pull the trigger and move on to the next chamber. If it clicks twice, you're either out of ammunition or the revolver is broken.
SP101 vs J-Frame
Well, the S&W is smaller. And it will most likely have a smoother trigger, right out of the box. However, the SP101 has a full-length ejector rod, which is extremely helpful when kicking emties to the curb. The 442 I carried for some time had the J-Frame's tiny ejector rod which works really well when the cylinder is perfectly clean. Just for the record, a 3" 357 Magnum will get you about 85-90% of the muzzle energy of a 4" service gun, which is still an incredible figure--not a "loud .38" as so many curmudgeons often say.
If I had it to do over again, I wouldn't get a 3" SP101 or a S&W Model 60 (their 3" 357 Mag). I would instead get a 3" S&W 686 Plus. That would be similarly sized to the SP101 3", but with a 7-shot cylinder.
So Why A Wheelgun?
Revolvers are inherently accurate, what with their fixed barrels and (typically) smooth triggers. Add in sturdy, wide sights, and you get a lot of accuracy for the platform size. That long, smooth trigger also makes me feel better in a pocket holster or a bellyband. Trigger protection isn't as much of an issue because it takes a concerted effort to pull all the way through.
There are some practical reasons as well. A 357 Magnum revolver is a wise investment because you can shoot 38 Special through it as well. If you reload (and you should), you can use cheap lead bullets over modest powder charges and shoot VERY cheaply. Also, because 38spl is so low pressure, the cases will last as long as you can keep track of them. When they crack, throw them away. I haven't had any 38s split yet. Additionally, learning to shoot a long, smooth double-action trigger will make you a better shot. If you can master that trigger, you will easily move on to other platforms.
Sure, revolvers have plenty of shortfalls. But if you know what you're getting into, they can still be very capable weapons.