When I was faced with this decision in the late 90's, I chose the 3913.
I'd been carrying an alloy-framed 3rd gen S&W as an issued pistol for several years and had fired several thousand rounds through it while working as a firearms instructor. I'd found the 3rd gen guns to be reliable, durable and more than accurate enough.
While I'd had my fair share of experience with the classic Sig's, I found the ergonomics, slim profile and general operation of the little S&W to be preferable for my desires and anticipated needs.
Both are fine compacts, though.
As time passed S&W has made continual improvements in their design, manufacturing and production, too. The TSW version of the 3913 is an excellent evolution of the 3913 series. I've often thought about calling back to try and find one of the current production 3913TSW's to supplement my late production 3913. (S&W often makes a number of overrun guns each time they make a production run for an LE order, and then keeps them back in their vaults for a while. They'll have them on hand if an agency customer decides to add more to an order, an individual cop wants to buy one from a LE distributor, or often they'll sell off guns from their vault to a regular distributor.)
I don't have an issue with the mag disconnect. I've spent over 20 years carrying issues 3rd gen guns and it doesn't bother me.
The manual safety/decocker doesn't bother me, either. I've converted a couple of my 3rd gens over to the spring-loaded, decock-only option and it's a handy feature for those trained to carry their weapons with the safety off in the ready-to-fire condition.
It's a shame that S&W discontinued the 3rd gen guns for commercial production, as the 3913 was probably just about the best example of state-of-the-art of a slim, single column magazine, 9mm alloy framed traditional double action compact as was ever produced.