Guys over TechnoBuffalo has posted a video showing iPhone 4 VS iPod touch 4G in a hot speed test. As it was noticed before that iPod touch 4G don't carry the same retina display as iPhone 4, also iPod touch 4G has 256MB RAM while iPhone 4 has 512MB RAM. Will this make a big deference? Let's see.
Despite the difference between iPhone 4 and iPod touch 4G's RAMs but thanks to the new A4 processor, iPod touch 4G performs well. The difference will appear when you a huge load comes over there, (say opening a lot of games / apps and using Multitasking, this will be faster in iPHone 4). Also the browser speed tests are very similar, sometimes iPod touch wins.