Can't answer the question re latency at 64, but the both products have tons of info available on the internet(starting with the main avid.com site). But you skipped over what is likely the most important detail and that is the fact that Native plugins will never be able to run in the "near zero" latency format as DSP plugins(meaning that neither product is likely to make things better for tracking with amp sim plugins, unless you can find a DSP version). Also, since either product represents a fairly serious investment(around $4K), your money might be better-spent on a Kemper or Helix to go with your current setup
The same applies to Virtual Instruments unless some companies start adding DSP versions to their products...