I applaud your dedication to ordering from a shop that provided samples. If you have the budget, that's such a nice gesture and helps keep local businesses afloat. As for installation, it may come down to whom you think can do the better job and who has a better reputation for warranty and follow-up in case anything goes wrong. Timing may also be an issue because the contractor and the flooring shop may have different openings, and delaying the sequence of your remodel for any reason could add expense. There is probably some more fact gathering to be done before you could make a fully informed decision.

Yes, you've hit upon some of the things I have considered. My guess is that the local dealer who has the relationship with the vendor might perhaps provide better service if anything goes wrong. Timing seems to me to be much easier to figure out if the contractor can just put it in his schedule whenever it fits.

If you think the local dealer has a better relationship with the vendor and would follow-up on any problems better, that's a huge advantage. Contractors can usually schedule in sub-contracted work as long as everyone follows through with the set schedule. The issue might be if the contractor was willing to let you do this since some contractors insist on a total-job control so they can make enough margin to make it financially worth their time to take on the remodel, understandably so. Be careful that he doesn't increase the price of his other work in exchange for letting you hire your own floor person.