I've tried or tried on REI Saharas, Columbia nylon convertibles, Ex Officio Amphis and Mt Hardwear Convertible Pack Pants. And my wife and I hike with ours on most of the time. No contest. The MH blows the rest away in function and comfort. The MH material is more water resistant, wind resistant, very breathable, very durable and super comfortable with chamois cloth lining around the hips. The Saharas are not bad, but are not designed as well and use material that's not as good, the Columbias are not made well and the material pills and wears out more quickly, and the Ex Officio Amphis are a thinner, flimsier material that rips and punctures more easily and are not as wind and water resistant as the MH. The Ex Officios are also not as comfortable on the inside and IMHO are poorly cut. They often look baggy on people. I'll add that while the MH pants are pack pants, the outer material holds up so well they look neat enough to wear while traveling in towns. Try to get a color that's in the brown range so that it doesn't show dirt off easily. You can usually find the MH convertible pack pants on sale at Sierra Trading Post or Campmor for $70-99.
Though I've never tried them, BeyondFleece has a custom cut pair of convertible softshell pants made of dynamic that look very high quality. Very expensive though.