Given that you specify that the temperature is within the range where summer tires are effective, the summer tires will generally have better wet traction.
Dry traction, wet traction, and snow traction are like 3 points on a triangle, the more emphasis you put on one, it takes something away from the other two. Technology can mitigate this to an extent, but given a certain level of tech, the tradeoff applies.
Summer tires, by specializing only in wet and dry and ignoring snow, are able to do those two things better. Some tires specialize so much in dry that they may be worse than some all season tires when it comes to wet, but a balanced summer tire like the PSS will out handle an all-season tire in the rain.
Here are two sets of test results
All Season Test June 1 2011:
Summer Test June 14 2011:
The Pilot Sport AS+ does slightly out-brake the PSS in the wet 94ft to 96ft (directional pattern helping perhaps?) but if you look at lap times, which combine acceleration, braking, and cornering, 31.37 sec/lap for the PSS not only beats 32.92 sec wet lap of the AS+, it beats every other all-season wet lap in the test, AND every DRY lap time posted by the all-season group.
Please note that I did not include the data from the 2012 summer tire test. Wet conditions on the track this summer were extremely slippery and results from this summer should not be compared with others. The two tests I highlighted ran the same cars, same course configuration, and same group of drivers within a two week span.
The 2012 vs 2012 results tell the same story, but the AS+ was not included in the 2012 results, so I used the 2011 testing to answer the specific example you asked for. All tires were much worse in the wet in 2012 due to the conditions, but the PSS wet time was again better than the wet lap times of every tire in the 2012 UHP all-season test.