Newer Avid Pre Versus Legacy Pre

I was wondering if anyone with experience with both the older Digidesign blue face legacy Pre and the newer Avid HD purple logo Pre can tell me anything about the difference in them. Have you used both and did you notice a definite improvement in sound quality? Do you know what was done electronically if anything between the two for improvement? I have been considering buying one or two of the newer model and wondered if it is a noticeable difference in sound quality. I currently own 2 each of the older model. I have done searches for past threads on this topic and can't seem to get anything to come up. I also haven't really seen any documentation from Avid explaining what the upgrades to the unit might have been when it was produced. I would appreciate any comments or advice anyone might have. I'm currently running Pro Tools 10.3.9 on a Mac Nehalem 8 Core 2.93 computer with HD3 TDM in a Magma EB7 external Expansion Chassis. Thanks.