Big difference. What you're talking about, I'm guessing, are regular laws/policies/regulations, etc. These can be changed or discarded with relative ease. To put something in the constitution is almost like putting in stone - meaning that once it's in there it's not so easy to erase it. Of course, all of this would mean a whole lot more if our leaders actually followed the constitution...
Relative ease in theory only. In actual practice what do you reckon to be the ratio of laws & regulations passed to those which are repealed?
I cannot remember the last time a federal law was repealed or allowed to sunset if it contained such a provision.