Best power source for Uno ?

Looking to make a project with a Uno as its heart, and only a light power load from the attached devices.

Wondered which power source would be best -

A 5V dc regulated wall/power pack fed into the USB connection; like those sold for tablets etc
or
A 9v or 12v dc regulated wall/power pack fed into the power tip socket.

The latter has the advantage of the Uno inbuilt regulator so can withstand any slight over voltage from the wall pack.

The former is a direct feed , so simpler, but any slight voltage increase and there is nothing to protect things, unless I say fitted a 5v6 Zener, or am I being too over cautious ?

5V into USB connector. Loads of cell phone chargers to choose from.
http://www.amazon.com/s/ref=nb_sb_noss/190-5901803-3103836?url=search-alias%3Daps&field-keywords=cell+phone+charger
Might need to add adapter to get to USB-B size (the big square one) if board is so equipped.

Or 7.5V into the barrel jack.
http://www.dipmicro.com/store/DCA-07510

ricky101:
The former is a direct feed , so simpler, but any slight voltage increase and there is nothing to protect things, unless I say fitted a 5v6 Zener, or am I being too over cautious ?

You shouldn't need a zener to prevent over-voltage; most if not all tablet/phone wall warts (chargers) - at least quality ones - have a built in 5 volt regulator. In most cases, this regulator is a switched-mode device (instead of the 7805 linear device found on-board the Arduino - which was used to reduce part counts and cost, mainly) - so it is more efficient and less energy is wasted as heat (which happens when you use a linear regulator to drop the voltage down - especially going from 12 to 5 volts, 7 volts of which get turned into heat, depending on the current drawn - and given that the heat sink on that regulator is the PCB - well, that can get very toasty).