Drupal 6, 7 or 8 for highest database performance?

I've tried searching, but am not able to find recent information on the topics that I'm interested in. So I appologize if I am repeating something that I just haven't found. But...

I've played with D6 and D7. But they were small sites on Hostgator co-hosted servers. I'm now working on a project that will eventually have a dedicated environment. My question is about performance for heavy use sites hosting complex data structures. Any graphics or video will only be for tutorials, so not a significant concern.

1. Does anyone have any performance comparisions between Drupal and other CMS systems that they can share? Have there been any performance comparisons between a Drupal and .Net environment (e.g. server load for heavy use sites)? Is there a type of Unix or Linux that is best for Drupal?

2. Given Drupal 6, 7 and 8 has performance been improving? (In my experience, D7 actually seems slower even on a simple site). Are there any performance tuning tips, tutorials, etc (I've already knocked out several optional modules on D7 and that helped, but doesn't bode well for performance). Again, my biggest issue will be holding complex data structures while a client is working with them.

3. Has anyone implemented drupal across a clustered / load balanced environment? Can you point me to any configuration gotcha's on this? Like does drupal handle failovers in the middle of a transaction well, since a user session will typically span a significant amount of time on the system I'm developing.

4. If I want to move some processing functions over to a java app on the client side, can someone point me to a start / howto on the topic.

Any help would be appreciated. If anyone is interested in doing a performance 'bake-off' between different environments, please contact me. I may be able to provide equipment to support such an effort around the end of summer. But again, this would only be for pure database and user interface performence... not graphics or video or other things like that... and the equipment would be re-purposed back to the project afterward (so the test environment is only temporary).

Thanks for any input.