I'm going to buy a phone which one shall I buy Xperia Z or Iphone 5s?

Tell me the advantage and disadvantages please…

I personally prefer Xperia Z
Depends on the specific use and your purpose!
LOOKS
Z1- Compact with a truly sturdy construction, one that is both water- and dust-proof, which is an important perk.
IPhone- It's slick, with a sturdy, aluminum corpus, and some seriously compact dimensions, thanks to that 4-inch screen. The frame, the home button that doubles up as a fingerprint scanner

DISPLAY
IPhone- It's sharp (325ppi), produces very accurate colors, offers excellent outdoor visibility, and leaves little to be desired, as far as viewing angles are concerned
Xperia Z- It's even more detailed (341ppi), thanks to its 720x1280 resolution, renders colors accurately for the most part, and looks great overall.

INTERFACE
Xperia Z- Android, functionality doesn't come at the expense of simplicity. The UI is kept relatively simple, and doesn't bombard you with an endless stream of options and tweaks, and is actually beautifully made.
IPhone- iOS 7 has been introduced, yet even the new, more colorful UI remains top of the class, as far as intuitiveness goes.

PROCESSOR AND MEMORY
Xperia Z- we've got Qualcomm's most powerful chipset right now -- the 2.2GHz, quad-core Snapdragon 800, with a speedy Adreno 330 GPU and 2GB of RAM.
Iphone- sounds slightly less impressive on paper -- a custom-made 1.3GHz, dual-core A7 chip with a PowerVR G6430 GPU and 'just' 1GB of RAM.

CAMERA
Xperia- 20.7-megapixel rear shooter, Outfitted with G Lens and an Exmor RS sensor, we regard this as one of the very best shooters currently available on a phone, though it isn't exactly perfect.
IPhone- the iPhone 5s' 8-megapixel snapper is much less complicated, yet produces some amazing results, thanks to the intelligent software. Moreover, taking great shots with Apple's flagship is both quicker, and simpler, and it has proven to be the slightly more reliable option.

5s is father of all phones