There are good reasons to criticize the new iPods touch: screen didn't grow (ok, some see it as an advantage), absence of Touch ID, no GPS, high prices but in some aspects the upgrade was, yes, significant. Starting with your processor.
There were years of waiting, but Apple jumped from a 32-bit A5 chip to a 64-bit A8 (with M8 coprocessor). The result you see in the benchmark shown next: 1,379 test points single-core, 2,440 in multi-core. Amazing: the fifth generation iPod touch scored 215 and 410 respectively, that is, we are talking about a performance ~ 6x higher.
Despite using the same chip as the iPhones 6/6 Plus, the clock iPod touch has been reduced from 1.4GHz to 1.1GHz, probably not to detonate the battery. It apparently has the same 1GB of RAM.
Other advances in the sixth generation iPod touch include improved cameras (just like the iPhones 6/6 Plus and iPad Air 2), Wi-Fi 802.11ac, Bluetooth 4.1 (the first Apple product to incorporate it) and a new version of 128GB. Due to these changes, it will have to be approved by the National Telecommunications Agency (Anatel) before starting to be sold in Brazil.