Colt's two models in DA/SA that shot .41 Long Colt are the 1877 Thunderer and 1889 & 1892 New Army & Navy, but I'm going to assume you were referring to the New Army and Navy model. They are very decent guns, not overly fragile but not tanks. Their internals are not impossible to work on, though spare parts are difficult to find. The 1892 and later variations have a better locking system for the cylinder.
The SAA are strong guns, fairly simple internally, newly made spare parts are easy to find as well as resources for working on them. Also, if you rechamber to a modern caliber you gain a cylinder and barrel of modern steel.
I think reliability wise the SAA is a better choice. For bush carry the DA is easier to reload, you can use Safari Land Comp II speed loaders for the K-Frame S&W, but you need to mod them slightly for .41 Colt. These can also be rechambered to .38spl but you need a Colt Police Positive barrel and ultra rare .38spl cylinder for the late model New Army & Navy.
If you were actually considering the Thunderer my advice is don't consider it. From my experience they are not even close to reliable and very difficult to work on.