I've hunted 17 for deer and seen alot of elk. They say that the Magdalena Mountains have nice bulls. A friend of mine guided some hunters in 15 last year and he swears by it. Two plus's right off the bat is its the GILA, MONSTER BULLS, the other is it borders Arizona fairly close to the White Mountains, another big bull area. I've also heard that there are alot of Outfitters but that don't mean nothing, its big enough of a unit to be successful! Good Luck!
unit 15 is my choice my family has hunted it a number of times with great success. let me know if put in for 15.
I hunt 15, mostly because it is a great meat unit. It does have a good supply of 300 class bulls and of course there is always a chance for a big bull but that is true for any southern unit.
If I were going for a really big bull 350/400 I wouldn't be in 15 and I am sure that many folks feel the same way! units such as 17 as you mentioned and a few other units have been producing some monsters over the last few years.