Singular

Why do I get different primary decompositions, and different sets of minimal prime ideals, using the algorithms
primdecGTZ (minAssGTZ) and primdecSY (minAssChar).????

It actually is for a very simple homogeneous ideal;

x^2 + y^2 + z^2, u^2 + xw + yz

characteristic zero, five variables.

Thank you for your help

The ideals are the same. You get only different sets of generators, due to the different algorithms.
You can check this by either computing a Groebner basis of the ideals or by applying 'reduce'.