best charging a/c or usb?

[coyote2]

Is charging via a/c adapter better or faster than with USB?

[CrowdAds]

[WalkGood]

Not that it's better or not but it's faster.

[robdean]

A standard PC USB port supplies 500ma. This is the maximum rate at which it can charge anything connected to it. Many mains-to-USB adaptors supply higher current (rarely a really dreadful one may deliver less!). 1000ma is common from such adaptors (it's usually marked on them) - an iPad 2/3 adaptor supplies 2000ma or more. That said, I'm sure there is a limit on the current the i9 will draw: whilst an iPad will draw 2000ma and charge around four times faster using its own power adapter, I doubt the i9 is able to draw even 1000ma. Thus there will be an upper limit on how fast it can be charged. If you leave it long enough, the full charge should eventually be identical no matter what the source so long as it's a source that offers the correct voltage - 5 volts dc.