It appears to me from reading tons of posts here and elsewhere that the JD-labeled attachments are generally well-made and solid examples of their type, but may be priced somewhat higher than equivalent good 3rd-party brands.
To that you can balance the merits of the I-Match compatibility Cowboydoc mentioned if that matters for your situation, the relative availability between brands of parts down the road (maybe way down the road), and possible pricing incentives that narrow the gap.
In addition you need to make sure you're comparing apples to apples regarding possible 'extras' that may come on the JD version standard (or to be fair, vice-versa).
I bought an MX6 rotary with my tractor. The MX6 is a decent medium-duty cutter, but at first looks relatively expensive compared to even a good aftermarket brand. However, there were rebates, discounts, package discounts, JD financing, and included features (slip clutch and full chains) that reduced a lot the initial perceived pricing premium.
As far as maintenance supplies - it seems that every time I see some test of a fluid, additive, filter etc.. the JD labeled choice comes out pretty good compared to 3rd party stuff. It may not be THE best but it will be right up there. And while it is almost assuredly at the high end of the pricing scale, it seems like it's pretty easy to trust if you don't know more about the other brands. Plus it surely can't hurt any warranty arguments you could get into down the road.