I've owned and carried both as duty guns - Sig P220 all the way. To my mind the Sig is a step above the 4506. It's lighter, I liked the Sig's sights and ergonomics, no silly magazine safety, etc. Overall I think the Sig P series in general is much more refined than the Smith autos.
To me, the Ruger P345 does everything the Sig P220 does without the massive hit in the wallet. The P345 weighs less than the P220. Both are 8+1 capacity. Both have accessory rails. Both still have factory support.
A good conditioned used P345 is a hell of a steal right now. The damn thing is the size of a Commander 1911 and weighs less than the S&W Scandium framed guns.
Thanks everyone for your input. I appreciate it very much. My computer will not allow me to answer everyone, so I am posting this reply. I tried to find a S&W 4506 but I could not find one, so I started looking for a Sig P220. The only P220s I could find were overpriced legions, carry models (I wanted a full size), some with contrast sights (I wanted night sights) and NOS all north of $1100. I did find a like new P227 in .45 acp at a reasonable price and I did purchase it. The P227 is just a P220 with a slightly wider body to accomodate the 10 round clip. So I am happily awaiting its arrival. I will keep you posted. Thanks again!
Strictly from an esthetics standpoint, the breech block pinned in a sheet metal slide by a roll pin really isn't a good fit with the price point. IMO
I have both a 645, & a 220. But my 220 says "Made in W. Germany". Big difference between that one, & what they sell now. Their guns have cheapened over the years. So to choose between a 645/4506, & a newer Exeter Sig, the S&W wins hands down. But if the Sig says Made in W. Germany, or Made in Germany, its a toss up. My Sig was imported in Herndon Va, before Exeter was ever in the picture. I've owned it since 1988.
While there have been some valid points made above, like still in production, the Sig series has some "issues" particularly if you're used to the 1911.
First, the Sig couples a (to me) short, heavy double action pull with a short, light single action pull. While you can learn to live with it, Jeff Cooper invented the "crunchenticker" moniker for TDAs when Sig was pretty much the only game in town. It fits. A fast, well placed, controlled pair is going to require a significant learning curve. I've never tried one, but I've heard a lot of very good things about Sigs DAO versions of various models. I don't know if this would interest you or it's available on the 220, but it does eliminate the point raised above.
Secondly, for a 1911 user, the slide release is where you're used to finding the safety. I struggled with the above 2 points during our service pistol trials in 1992.
Third, at the 25 yard barricade, the 220 literally beat me (my hands) bloody.
Strictly from an esthetics standpoint, the breech block pinned in a sheet metal slide by a roll pin really isn't a good fit with the price point. IMO
If you look around, you might find some other option that you might like better.