So I did a little more research. I took a look at what TireRack offered as far as Xi2's and Xi3's. I found that there is no overlap in sizes across the 2 models. They have about 50 different sizes in each model, but you can't choose between the 2 for any specific size. I called them to find out what the story was.
At first I was told that the Xi2 was basically discontinued and the Xi3 is the replacement. "I'd be surprised if we still carry much Xi2 inventory." When I pointed out that there was just as many Xi2 sizes to choose from as the Xi3's, he changed his story. "Oh, those are the Latitude Xi2's which are different from the previous Xi2's.
"OK" I said. "But that doesn't explain why there is not a single size available in both models. If the Latitude is not the same as the previous Xi2's, then the Xi3 isn't really the replacement for the Latitude Xi2, is it?"
New story:
"The Latitude Xi2's are mainly for SUV's and light trucks and they only make them in sizes that they aren't going to make in the Xi3's."
Me: "From what I understand about tire sizes, I'm seeing sizes that fit both passenger cars and SUV's in both the Xi3 and Latitude Xi2. So the models overlap in vehicle type usage but not in size."
That's when I finally ferreted out the true story:
"We don't carry the same sizes in both models because they don't want competition across the 2 model lines."
OK, so now that I finally got that cleared up, I asked him about the Laufenn snow tires vs. the Michelin Xi3's, which are available in the size I need:
"We do not carry Laufenn snow tires, but we do carry a few Laufenn all-season models. Based on what I know about the Laufenn all-season tires vs. Michelin all-season tires, I would strongly recommend the Xi3's over any Laufenn snow tire."
Now, I could have said "Well, of course you do. You carry the Xi3's but not the Laufenns, so you are going to recommend what you sell, not what you don't." I could have said it, but I didn't. Bottom line is that I like the Xi2's that I've used so I have no reason to think that I won't like the Xi3's.
Finally: TireRack price vs. Discount Tire price
1 - The $70 rebate is available from both vendors.
2 - The additional $50 rebate is only available from Discount Tire if you purchase the tires with their Credit Card.
These tires are actually going to be purchased by my daughter as a gift for her partner. She really doesn't want to apply for a new credit card just to save $50. (Her credit is fine but she has been a victim of identity theft and is very cautious about who she gives her information to.) Therefore, I am going to purchase the tires through TireRack since I already have an account. I will pay the full price ($447), keep the $70 rebate ($377) but only "charge" my daughter $327, essentially covering the $50 rebate.
Thanks for pointer to the Xi3's.