Is it better to update via Itunes or over WiFi?

I'm fairly new to having an Iphone (have a 5S which I got last June) so I've gone through the IOS update process a couple of times. After reading up on the update process - I did each update with my phone plugged into my laptop using Itunes. I've noticed that when a new update is available, my phone will say that it is downloaded already and I'm assuming that if I chose to do the update over WiFi - it would just install it. My question is - which is the better/safest way to do the update? It seems to take quite a long time when I do it via Itunes and I was wondering if it is quicker doing it via WiFi? How do most people accomplish the updates, Itunes or WiFi? Thanks for any input you'd like to share!