I like the Pulse+.
You get 30 seconds where you can leave the Taser on the ground while it immobilizes the attacker for 30 seconds.
You can try to call 911 in that 30 seconds as you flee, but there may also be more than one attacker.
The Pulse+ will summon police to the scene as soon as you remove the Taser from the holster and disable the safety. That frees you up from trying to multitask.
Cops have policies that they won't try to use a Taser or other nonlethal/less-than-lethal weapon without backup. These tools aren't as effective at stopping threats (especially those with chemicals in their systems) as a firearm. So, have a plan B. I think "Shoot, drop it and use your 30 seconds to run for safety" is viable depending on the circumstances.
If you don't announce you have a Taser, the attacker/s might think you have a firearm and flee, so that's another thing to consider.
No matter what Taser you decide on, training should be a priority. Using one requires a unique understanding of when, how and whether to employ them. If you try and Tase a 400 lb Samoan linebacker, you might be the one in for a shock when it only makes him angrier!