Is it better back up my iphone 6 with computer or icloud

I wanted to sell my iphone 6 but i want all my data on this current iphone to appear on my new iphone 6s+

So is it better to back up my iphone on icloud or computer ? And which does make my data will appear on my new iphone ??

But my new iphone isnt arrive yet so i just want the data save so when i get my new iphone i could connect the data