I know this is a necro thread, but I've tried the stock A2/A5 combo, a UOA5 bridge with an A2 neck, same with an A3 neck, and I've settled on UOA5 for both pickups. There are a lot of reasons, but the main ones are these.
The UOA5 in the bridge gives it a nicer, warmer character, losing the shriller high end of the stock pickup and balancing out the tone to my ears. It sounds thicker, more balanced and somewhat warmer. It also reduces output, but only slightly, and therefore makes it a more vintage-sounding pickup, but still hot enough to be what it is -- a higher output humbucker.
The UOA5 in the neck has somewhat of the opposite effect. It retains the A2 character, with nice midrange and a vocal quality, but it gives enough of an increase in the high end that it makes the pickup clearer. I've said before the UOA5 in the 490r does Slash better than the Slash APII does. Very, very nice pickup with this magnet. It also increases output, but only slightly, balancing the set much better than the stock A2/A5 combo.
If you have this set in a Les Paul, I cannot recommend the UOA5 in both pickups highly enough.