The taser model that i once used, the effective distance was i think 15' and a one shot deal firing two probes simotainoulsy. Was trained to use it as a contact stun gun in case the probes missed the bg--what we called a "drive stun"----drive the point of the prongs into the bg and stun should the probes miss or miss-fire---which is always a possibility. Or again use it as a contact weapon if facing more than one bg. Cost back then to us was $15.00 for that one shot of prongs---don't know what it is today but it quickly beomes cost prohibitive to practice unless you got deep pockets like an agency. Does require a degree of shooting skills and aiming with a mush trigger. If you miss, you are back in the same boat of having to be in contact distance to use it. There is a manual of arms that you need to learn as far as handling a miss-fire and reloading.
Fear factor is high. In useage, however, the suspect is extremely angry and pis*** afterwards. Suspects have been known to be back in the fight after the stun which is why taser training keeps mentioning the ability to keep applying juice to the suspect to keep him down. At some point depending on location and circumstances, the wife is going to need to get out of the area. Once contact is broken, she is left with a contact weapon against on very pis*** bg or a contact weapon against his partner unless she can reload the taser under stress. The bg will still have hand/eye coordination and able to use a weapon afterwards.
With oc spray, the bg will also be pis***, but he will be temporarily blinded for around 10 minutes and not able to pursue very well at all or be able to aim a weapon much to fire at her since he will have exteme difficulty in seeing and breathing. It can handle multiple targets better than a taser should it be a group attack. It is much less expensive and you can practice with it more and requires less accuracy standards. At one time we had "inert" practice cans of oc for training--don't know if they still make these harmless practice devices that discharged a harmless spray any more but they enabled practice indoors for delivery.
As with any weapon be it taser, oc, gun, knife, or whatever---once in a blue moon you'll run into that bg that just doesn't give a da**. It happens.
As you can guess, I am a stronger advocate of oc pepper spray. I have used it with probably a 99% sucess rate as i don't ever believe anyting in 100%.
Best advice i can give would be to supplement what ever defensive system you go to with some self defense classes.
