Both are lightweight running shoes for people who have a fore-foot strike.
The Newton Motion is double the price of the Kinvara 2!!
After running with both, I find that I preferred the Newton over the Saucony simply because there is more cushioning and more 'springy' feel to the shoes - That is provided I am running on a relatively flat surface like East Coast Park. but if running on roads, I think the Kinvara 2 is a better choice.
Although my preference is towards the Newton, the Kinvara 2 actually is still a very good pair of shoes - it holds up well as a trainer and also as a race day shoe.
The next thing is to see how durable both shoes are, I'm alternating between them and see which one wears out faster. I do hope that the Newton hold up better as it costs twice as much!
Now I'm deciding which to wear during the Full Marathon.... ???