Let's assume, for the sake of argument, that we're talking about real-deal Tasers, not some alternative or Stun-Gun type thingy.
1. Tasers have a one-shot capability, unless you carry multiple cartridges. Even if you DO carry multiple cartridges, you have to analyze the failure to stop, recognize the solution, remove the used cartridge, insert the new cartridge, aim and cycle the weapon. Want to try that in the midst of a Tueller Drill? Me neither.
2. Tasers have an unacceptably high malfunction rate for use as a primary weapon. It's not horrible, but it is bad enough. If it was a handgun failing like that, you'd sell it. Hangfires are particularly prevalent.
3. Nothing is a 100% one shot stop, and neither is the Taser. The beauty of a handgun is that if the first round fails to stop, you have several more on tap. If the Taser fails to stop...you can...throw it at him. Actually, you can drive-stun him (use it like a stun gun), but that is decidedly unfun, and removes the Taser's two biggest advantages, range and muscular incapacitation.
A TASER IN "STUN GUN" MODE IS ONLY PAINFUL...IT DOES NOT LOCK UP THE SUSPECT'S MUSCLES.
4. The Taser is fragile. Battery packs get knocked loose. Cartridges get broken and disgorge their guts.
5. The civilian versions cycle for a longer period of time than the LE versions. You're supposed to zap the BG and run like a scalded monkey. If, however, you are still in the area as soon as the cycle is up, lookout. He is no longer incapacitated (
AT ALL), and will be more than a little annoyed with you. a 30-second (IIRC) head start is a pretty good advantage, though...and to tell you the truth, if I rode a taser for 30 seconds, I'd just want to curl up and die in peace.
You can keep your wallet.
It bears repeating, though; electricity works like flipping a switch. ON, and he is incapacitated (assuming you got a good hit and he's not one of the very few people who are resistant to the Taser). OFF, and he is back to 100% (at least physically). It is that fast. When that thing stops, the game is back on.
6. The Taser is designed to be used by LE in a situation where lethal force is NOT indicated...OR, in a situation where lethal force is indicated, but there is an opportunity to use a less-lethal tool. That "opportunity" implies not only the time to use it, but also the resources on hand to use it safely. Those resources include one or more other officers with lethal-force cover. If the Taser fails and the BG presents a threat, he gets shot.
The Taser has been marketed to civilian market as an alternative to a handgun, and IMO it is not a very good one. If lethal force is not authorized, you probably should not be Tasering the guy. If lethal force IS authorized, you should certainly be shooting him. It might be better than any other legal option for some areas (*cough*NYC, DC*cough*), but if I had the choice of a handgun or a Taser at my hip, I'm picking the handgun. But, as was said, a Taser in hand beats harsh language. If it is the only choice you have, go for it. It is a great, if imperfect, tool.
Mike