The quality of life all over Manhattan is good depending on your interests and income. Ultimately it comes down to what you're looking for. The Lower East Side is a younger, artsier area with galleries, bars, and lots of nightlife. The Upper West Side has some of this too but it also has more in the way of estbalished arts with Lincoln Center, Merkin Hall, and Symphony Space. Riverside Park is right there as is the crown jewel of New York City parks, Central Park. It's probably more family friendly and quieter.
As far as property values? The Upper West Side is largely a bit more expensive, particularly when you get near Central Park and it becomes the domain of the richest people in the world. However, many people live where they can and depending on size, views, outdoor space and many other variables, you can spend equal amounts in both places.