The only feed we can get locally is the La Coop layers feed. Today I was out of town and drove by a Purina feed store and got some Purina feed. Is the Purina feed worth the 1.5h drive or is the La Coop feed just as good?
You should check out PoultryDVM.com ... they have a tool which lists all the types of chicken feed and lets you sort by different properties. http://www.poultrydvm.com/feeds.php
There shouldn't be much difference nutritionally. If ingredients matter to you, I'd get a list from each manufacturer.
IMO, 1.5 hours is a long way to go for feed.
The difference in the particle size is most likely either a difference in the crumbler equipment at each mill or the type of binding agent used to make the pellets.
Another important factor is age. Each bag of feed will have the manufacture date. If there's a significant difference, shoot for the freshest feed.
Some feed stores will keep feed till it sells. Some will do what it takes to move it before it gets old. A lot depends on how much they buy at a time and how many customers they have for that specific feed. The more they buy, the better their price.
Once ground, grains lose their nutrients over time. The vitamins, if stabilized, should last a while. Minerals won't be affected by age.