What I see as a negative is there are so very few pistols that offer a second strike. Also, takes a new level of training. I would think if the second strike doesn't do it, try a 3rd or 4th, which does take time away from slapping and racking.

So it's only a negative in my mind if one overlooks dozens of excellent pistols that don't have it for one that does. Looking for second strike exclusively limits one's choices.

Since almost no (maybe absolutely none) LE agencies have pistols with second strike capabilities, it's worse than useless to teach it with Glocks or S&W pistols. What's the point? They're incapable of second trigger pulls. Same with the 1911. If an agency DOES issue weapons with second strike capabilities, then teach pulling the trigger again, I suppose, but slap, rack, bang is a better solution.

Edited to add this link.
Do You Need Two-strike Capability In Your Pistol?