Am I missing something, or is “Orient to Curve” option missing from ExtrudeCrvAlongCrv cmd? I’m using the latest Rhino for Mac. Basically I want to make sure my profile crv is maintaining its full shape along the length of the extrusion (thus maintain constant volume/area of the extrusion). I see that Sweep1 gives the results I’m looking for (it orients the profile along the extrusion), but I think it would be more intuitive if the ExtrudeCrvAlongCrv cmd incorporated this option as well. It would need to do “mitering” of course 
thanks! -d
The difference between Sweep1 and ExtrudeAlongCurve is precisely what you mentioned - with Extrude, the profile orientation is fixed, whereas with Sweep1 it orients itself along the rail. This is intended behavior and why there are two commands instead of one with two options.
–Mitch
Good to know - thanks!