I'd look to Sony's compact series. They seem to go for small-ish displays without compromising on specs (see both the already released Z1 as well as the upcoming Z3)
Unlike other manufacturers, the international editions of Sony phones have all of the HSPA+ and LTE bands to work well on AT&T and T-Mobile and these days you can get back the extra upfront cost of buying an unlocked phone with monthly savings. International unlocked phones also generally qualify for Sony's boot loader unlock program. And you often can even get a good deal from a SE Asian gray market exporter.
