There are lots of incremental improvements that eventually amount to something major, depends on how old is the device you're coming from. Compared to my Nexus 6, the Pixel XL is a major improvement.
Those phones are mostly the same. The Pixel XL is slightly smaller but offers a premium design and improvements in hardware, including a faster processor and more RAM.
Both offer pure Android, but the Pixel receives a handful of exclusive features.
At least for me, i believe that i will not switch phone for another year. Pixel is a bit overpriced at that range ( as iphones ). I expected it to be at least a bit cheaper.
Either i will wait a few months to see if the prices drops for the pixel or wait for the next year phone.