Let's start by saying that we are not completely against those big box stores out there. They have their advantages from time to time. We will do our best to not mention a specific store but we can't imagine that any of you have never been in to one of them in your life.
Here's the deal, we aren't big fans of purchasing a lot of items for a remodel in those big stores. Beyond the pricing, it's the things you do not see that may be your downfall. For example, you can certainly find a great price on a good looking kitchen faucet in one of the two largest home improvement stores in the country. But you are paying for something that is loaded up with a lot of plastic "guts" and won't last as long as it should or could, even if you take great care of it. Now, with that said, the big stores do have some options with the great high-quality insides, but those items are going to be priced similar to specialty stores and they may not have the largest selection. They tend to make more margin on the lower priced items that the high-end ones.
So how are you to know if you are getting a good product? First, read the back of the packaging. Look for plastic fittings, or do an online search about it. Don't go looking for the least expensive option. Saving money is great but long term it may come up to bite you on a costly repair or simply having to replace the product again. Another option? Go to one of your local specialty stores that deal with just one product like kitchen faucets or bathroom remodeling items, etc. Stick to the nails, lumber, screws and tools at the big box stores, don't skimp on the plumbing.