Will there be a performance benefit in the upgrade for iPod touch 5 to iPod touch 6 for the KNFB reader? A totally blind user wants to make use of the KNFB reader but does not want a cell phone, some of the reviews I have read suggest that it works best on the iPhone 6, other reviews suggest that that iPod touch 5 is a suboptimal version of the iPhone 5.  I have near zero knowledge about smart phones and less about apple devices. 

Is it possible to tell if an iPod touch 5 will provide the same level of function with the KNFB reader as users are seeing with the app on the iPhone 6?
There is no iPod Touch 6. In fact, the iPod Touch hasn't been updated in 2 years and even at launch did not have as good a camera as the the iPhone 5 it was introduced with (the iPod Touch camera is coverable to the iPhone 4S or maybe even the iPhone 4?). I can't speak about the KNFB reader specifically, but the newest iPhone (6 and 6 plus) are much faster than the iPod Touch 5 from 2012, so no, the older hardware in the iPod Touch 5 cannot provide the same level of functionality.

Whether the functionality in the ipHone 6 is enough of an improvement to make the cost worthwhile is a question only the user can answer.