The 459 is a 2nd generation S&W. The 59 was the 1st gen S&W.
I carried the 459 below as my duty gun from 1982 until 1989. Our issued gun was the 439 but for those of us on SWAT we were permitted to carry a 459 if we bought our own. I sent mine back to S&W and they did a great tune up on it. I've run thousands upon thousands of rds thru it over the years and never had 1 problem of any kind. I went to plain clothes in 1988 and carried it for about a year until we were issued a 469 then the 459 was carried in my squad as a 2nd.
As far as pros - mine shoots really well. Never had any kind of malfunction using all kinds of ammo from dept reloads to +P+. It's been carried in all kinds of weather and conditions.
Cons - I don't like the straight backstrap on the factor guns. As you can see I fixed that by installing a curved backstrap which gives it a whole new feel that I really like. That's the only "con" I had with it.
I don't carry it as much anymore. It's still a large gun and during the summer it's not as easy to conceal. It still gets drug out a few times a year and carried.