I've purchased several phones for myself and others (Sony, Motorola, Samsung, LG, Huawei) over the last six months. Buying cheap for best value for money often means looking at clearance products. For example, two months ago I bought two clearance phones for under $200 each, the Sony is on Skinny and the Motorola was on 2 Degrees prepay and is now on a Vodafone plan: http://www.gsmarena.com/compare.php3?idPhone1=3998&idPhone2=4098
GSMArena.com is a good site for phone reviews and specifications. Pricespy.co.nz is a good place to compare NZ prices and specs. I've found retail store clearance prices were most often best at Dick Smith and The Warehouse/Warehouse Stationery but clearance products aren't on Dick Smith's website anymore so I've had to look in store.
I'd look at these criteria for choosing a phone:
Android version is very important. Both came with 2.3 but only one was vendor upgradeable to 4.0 which is much better and easier to use.
Screen clarity which is based on a combination of screen size and resolution, contrast and brightness The Sony 3" screen is actually a lot clearer to use than the Motorola 3.7" screen even though it has a higher resolution.
Screen size. Bigger is usually better except battery usage usually goes up.
Processing power. Both phones have same RAM and processor speed but the Sony loads apps much faster.
Size. A smaller screen means a smaller phone which fits in my pockets a lot easier.
Controls. Simple things make a difference like the location of the ON button: side or top. The Sony has it on the side which is easier for me to use. The Sony is also asymmetric so I can always orientate it correctly to press the correct buttons even when I can't see it.
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