Except hes looking for a small form factor Android phone, roughly the size of a iPhone 4s, not a phone that has to be smaller than a 4s.

OP, grandparent is correct, I was in your situation and a 5X was perfect. Pixel and Pixel XL look like they'll be too big, but you should wait for the October 4th event to confirm.

And probably slower than an iPhone 5s. Honestly I don't really understand how is it possible that google throws out a phone that is slower than is predecessor (the Nexus 5) and still manages to sell a huge amount of devices.