You might not notice any difference, but on the other hand you might create a grossly overpressure load. The rule of thumb, and it's a tried and true rule, is to back off at least 10% whenever you change any component. Changing primers of any type or variety, even if you change from one manufacturers standard primer to another manufacturers standard primer, certainly qualify for following that rule.
WLP's are slightly less powerful than magnum primers from most other manufacturers. They can be used for both standard and magnum loads, but you should definitely back off 10% if you go from a WLP to a different magnum primer.