The heavier bag may great for spring/fall but what about summer?
When do you do most of your camping?

You can make the lighter bag warmer by adding layers. But do you really want a 0 degree bag in the summer? You'll be hauling a lot of extra weight and bulk just to be too hot at night.

IMO a 3lb 110z bag is too heavy for 3 season backpacking. And keep in mind that those numbers are the manufacturer's claim and the actual weight will likely be more.
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If you only travel on sunny days you will never reach your destination.*

* May not apply at certain latitudes in Canada and elsewhere.