Based solely on the client spell file, I can't seem to find much of a difference besides the duration (as noted), the fact that SKs get the spells 10 levels apart, and that the recourse for Shadow Vortex has the AC increase in slot 7 while the recourse for Shadow Creep has the AC increase in slot 1.
This might only mean that the difference might be something that I cannot see in the spell file. For example, if the recourse goes to your pet instead of you, I'm not sure if that would be listed (doesn't look like it). The recourses themselves don't mention a pet, but I have little experience with recourses and their targets.
You could determine that theory fairly easily with a quick test. Testing is far superior to relying on the spell file!