I need advice on smartphone

[PabloDons]

depends what you are going to use it for.

if it's for gaming and general application management, I would suggest iPhone because of the appstore. There's nothing you can't find there.
if it's for daylight picture taking I suggest Samsung galaxy because of the freaking awesome camera.
if it's for nighttime picture taking I suggest Xperia because god fucking damnit is it impressive in dark (also 4K video capture)
if it's for multitasking and working I suggest Android because it's openness and general features like multiwindow mode participate a huge part in making it the most amazing OS.
if it's for heavy usage and battery dependence I suggest Samsung galaxy because of the replaceable battery.
if it's for camping and outdoor/moist usage I suggest either Samsung galaxy or Xperia because they're both IP67 certified (water and dust resistant)
if you want a big screen Samsung Galaxy Note is your best bet because it's strong, durable and it has android (wohoo!)

you can't choose phone by size and specs only because chances are you're not going to get what you wanted