Brandon Chester, writing for AnandTech:

It’s really not difficult to come to a conclusion on the iPhone SE. It’s clearly the best 4-inch smartphone on the market, and you can ignore all of the specs when making that assessment because it achieves that by virtue of being the only offering at this size. For the sake of comparison, you can take a look at some Android devices that are larger than the SE, but smaller than your average Android smartphone.

And:

Even when you consider the smallest high-end devices from the Android manufacturers, it’s not hard to see that the iPhone SE comes out on top. Apple’s A9 SoC is still one of the fastest chips you’ll find in a smartphone, and it goes without saying that the Snapdragon 810 SoC in a smartphone like the Xperia Z5 Compact really isn’t comparable in the slightest. Based on my experience, the camera is also unmatched at this size and price.

A remarkable review, a wealth of detail.