Matt in AK,
If I had to pick, I would definately go on May 4th & 5th, there are just more bears out and about the first two weeks of May. But, because of the lower then normal snow on the ground this year April 25-27 could be pretty darn good also. If you hunt in April, I'd suggest hunting South facing slopes / mountains, snow will be melting off those areas first. Also, having an extra day to hunt by going in April is a good thing! But, as I said earlier, if I had to pick I'd personally go in May. Since you only have two days then, maximize your time by being out there at first light & hunt till it's almost to dark to see to shoot. Good luck & be careful out there!
Del