Memorysize in resourcepool

Memory size for pool1 is 10% and pool2 is 20% and maxmemorysize for both is 90%. When run using an user in pool1 the query takes less time than the same query run with user in pool2. Shouldn't the pool2 query run faster coz its initial memory is higher than pool1? If 2 queries are run in parallel from one pool will the memory allocation be half the actual size?