Just a few thoughts...
OC--- Its affect varies depending on the person. Some people are not affected in a strong way with OC and may continue to fight even with a proper application of OC. A large number of people will be affected by OC though, and its generally the main less-lethal that I recomend to people. The resulting discomfort caused by OC takes time to go away, and at least when I have had OC applied to myself in training, it takes probably 20-30 minutes to get back to some what normal conditions, and during the 20-30 minutes I had to do alot of irragating my eyes with cool water and using baby shampoo as well on the areas it contacted my skin. My sensations included: intense pain in my eyes to the point of barely being able to see while squinting, my face felt like I shoved it ina 400 degree oven and slammed the door, and I had a level of breathing difficulty, though as part of the test also, I had to fight through an obsticle course. Kinda hard to do when your mostly blinded, lol.
TASER--- TASER is one brand of ECD, and it has its own short comings as well. First of all, its important to note that depending on version a ECD can have either a 5 second time duration, and others have a 30 second time duration. Also, for the ECD to have a proper affect of disabling a threat, it needs to have both of the probes into the skin. Such things as heavy clothing can reduce, or stop the ECD from doing its job properly. It is also a single shot, though there are bulky multi shot models slowly coming out. Once the ECD is applied, it can be re-applied until the battery weakens. Also, the TASER brand ECD's I have been around have the ability to do a drive stun as well. Also, the TASER brand ECD's do have a memory and it can be downloaded by TASER if needed for a trial. I believe the memory is rather limited to how many times it has been discharged (applied). As to what happens from my experience. It was rather minor, almost no pain, just felt like 99.9 percent of my mucsles felt like they locked up. At the end of the 5 seconds there was no pain. Actually it kinda felt like I was tickled in a way really. After the end of the 5 seconds I was instantly able to return to a fight if I had needed.
My personal views--- I feel that OC is the better option for most everyone who desires a less-lethal option. Thats because that the OC takes a longer time to wear off, it allows it to be used with multiple attackers and also allows the person defending theirself to run away and seek safety. With an ECD either you have to stay some where close by so the leads will deliver current from the ECD to the probes, and then its only for 5 or 30 seconds an application. Also, with an ECD, there is a question of who will eventually remove the probes, as well as if you apply an ECD and then run, whatcha gonna do when the leads run out during the 5 to 30 seconds of time it delivers the shock? If a person uses repeated applications of an ECD I am unsure how it would look in front of a jury. The length of the leads, its basically a one-cartridge per attacker and the limited duration of the ECD is why I do not recommend an ECD. The only good point I see toward an ECD is that there is not the decontamination thats required with OC when the law enforcement and medics arrive.
Though I have access to both OC and ECD, I do choose not to carry either. Just my personal view.