[rules-users] Indep stated Sub Conditions Vs AND

Whats the difference between: when <Sub Condition A> <Sub Condition B> Then ... End Vs when <Sub Condition A> and <Sub Condition B> Then ... End ..Assumping I have no need to use variables between A & B, do I get a performance improvement using "AND" or does the Rete evaluate faster if the sub- conditions are stated independently? Thanks in advance