Hi siuyickyick,

Are you referring to the LG Optimus G or the Optimus G Pro?

Assuming that you'r ereferring to the Optimus G, when it comes down to processing power, the HTC One is the most powerful of the three. Both the Optimus G and the Xperia Z have similar processors, both of which are part of the Snapdragon S4 Pro series, boasting quad-core architecture and a frequency of 1.5 GHz.

Quite powerful (the S4 Pro being the most potent CPU of year 2012), but the newest Snapdragon 600 quad-core processor in the HTC One is newer and even more powerful. The architecture is newer, and the frequency is also higher (1.7 GHz). As far as RAM and graphics chip, all three smartphones are pretty similar. They have 2 GB of RAM and an Adreno 320 GPU each.

As for battery life, I haven't tested them so I couldn't say for sure. However, based on the information provided in spec sheets, all three smartphones are more or less on equal ground, depending on the task. The Optimus G has a 2,100 mAh battery, the Xperia Z a 2,330 mAh unit, and the HTC One is powered by a 2,300 mAh unit.

To give you some numbers (may vary, of course)

HTC One:
Stand-by Time: Up to 500 h (2G) / Up to 480 h (3G)
Talk Time: Up to 27 h (2G) / Up to 18 h (3G)

Xperia Z:
Stand-by Time: Up to 550 h (2G) / Up to 530 h (3G)
Talk Time: Up to 11 h (2G) / Up to 14 h (3G)

LG Optimus G:
Stand-by Time: Up to 456 h (2G) / Up to 411 h (3G)
Talk Time: Up to 15 h (2G) / Up to 13 h (3G)

In case you were referring to the LG Optimus G Pro instead of the original Optimus G, then this handset has a larger battery - 3,140 mAh - but it also has a larger display - 5.5 inches - so it balances out on the most part. As for GPU and RAM, it's the same Adreno 320 graphics chip and 2 GB of RAM, but with a Snapdragon 600 processor, same as the HTC One.

Optimus G Pro Battery:
Stand-by: Up to 576 h
Talk Time: Up to 15 h 30 min

I am using iphone 4 and want to change a new android phone. I am wondering which of these would be suitable for me. I want to know which of these has the longest battery life for daily use and fasttest processing power