[dhodgeh]

Got an upcoming trip to the SW United States (Arizona/Utah border - Page, Kanab, that area).

Landscapes will be the major subject matter.

Got room for one larger than normal lens. Choices are the DA* 300 or a Sigma 180/3.5 DG APO Macro.

Rest of the kit will consist of primes ranging from 8 to 135 mm.

Which of these two lenses would you take?

[Macario]

If landscape is the major factor, you don't need to bring either of those lenses. You are already completely covered.
But if you still want to take one of those lenses, it depends what you want to shoot besides landscape. Wildlife, take the 300. Macro, take the sigma. If in the other lenses you are taking you already have a short macro, I would take the 300 (unless you want to shoot bugs etc macro, then the sigma is advised)

[contrabass]

If it were me, with all those wide-open spaces and the list of lenses you're already bringing, I'd bring the 300mm.

"Landscape" doesn't automatically mean "wide lens". Some of the more interesting landscape photos I've seen recently were taken with telephoto rather than wide lenses.

Don't forget how utterly immense the spaces are in the southwest. 300mm might give you a viewpoint that everyone else is missing when they're busy zooming all the way out to 10mm to "get it all in".

[Lowell Goudge]

I would agree with the other posters, Although there is a tendency to try to fit it all in, unless you are really into doing weird landscapes with huge foreground to background size differences, the fisheye will not get a lot of use.

When I did utah and the grand canyon, I had 18mm on film as the widest, and 300mm on digital as the longest, and felt I could have used a longer lens.

[jatrax]

Agree, that is big country, take the 300mm.

[hoanpham]

300mm.
It's hard to climb to a view spot to take photos. But when you got up there, 300mm will be the best choice.

[RioRico]

My initial thought was for the 180. But since you're otherwise covered up to 135mm, I'll agree that the 300 makes more sense. Just be aware that air in the Arizona-Utah border country isn't always clear, thanks to a few major coal-burning power plants, also thanks to thermal convection on hot days. Get up early for longer shots. I hope your're planning to shoot along the Mt Carmel Jct - Zion NatPark route, really splendid country. And nothing beats the heat like overnighting up at Cedar Breaks NatMon, up in Bristelcone Pine realms. Have fun!

[Frank B]

I drove through that area not too long ago (December of 2011) and a 300 would have been nice to have at times. I think you would find it useful for isolating parts of the landscape,

If you get to Navajo Bridge you should get some good shots of the condors with the long lens.

[zapp]

Got an upcoming trip to the SW United States (Arizona/Utah border - Page, Kanab, that area).

Landscapes will be the major subject matter.

Got room for one larger than normal lens. Choices are the DA* 300 or a Sigma 180/3.5 DG APO Macro.

Rest of the kit will consist of primes ranging from 8 to 135 mm.

Which of these two lenses would you take?

Take whatever you prefer. There is a reason why you bought the 300 and there is a reason why you bought the 180. Make up your mind if you want more tele or more macro. You can not really say that the SW US is tele or macro land....