Thunderbolt 2, USB 3, Gigabit Ethernet, 4K Support, Firewire 800, Sound Ports
MacBook Pro i7 Software Development Performance (XCode)
See the system configuration notes.
Apple XCode build DiskTester
This is a CPU intensive test that is not influenced by disk speed (smart I/O and caching hide the I/O speed).
The Core i7 offers a 20% performance improvement, and this is one test where hyperthreading helps; running the test and limiting XCode to 2 threads results in 140 second runtime, suggesting that clock speed is also important here.
Developers: you can control the number of threads XCode uses while building:
defaults write com.apple.Xcode PBXNumberOfParallelBuildSubtasks 4