I don't have too many suggestions for you, but I thought I would give it a shot anyways. First of all, Apple does not monitor these forums. All of us here are only end users like yourself trying to help one another out.
How much free space is available on each of these devices? I'm assuming it is a sufficient amount?
After restoring completely to factory settings, did you load ALL of your content back onto the device or did you start with small portions of it to see if any of the Apps were causing the issue?
Wipe it then loaded to OS No other apps installed yet Accessed Safari same thing Slow access Loaded some music and accessed the Music app White screen for 4 seconds before playlist opened With one playlist and 3 songs. This is not going well. Went to the apple store to talk to them about it. There were 4 other people there with the same issue and the Staff said they get people in all the time and they have reported it to there support. Oh well Will have to wait for the next patch.