The first difference between the MileagePlus X app and the United Shopping portal is that the app is so much easier to access. What makes it so useful is that you can earn points when you are physically at a store paying at the point-of-sale. The Shopping Portal, on the other hand, requires you to do your shopping online through your computer.
The other difference between the MileagePlus X app and the United Shopping portal is that you are buying two different things. Purchases through the mobile app are in actuality a purchase of a gift card that you will immediately redeem. The shopping portal, in comparison, has you directly buying products through the website.
If you want to be extra clever, you can triple dip by using your rewards credit card to buy a gift card through MileagePlus X and then use that gift card to purchase through the Shopping Portal. I would do this in situations in which I would be more deliberate with my purchases, which Christmas shopping has not been.
This brings me to the reason why the MileagePlus X app has made holiday shopping different for me this year. First, it makes me more mindful of where I go shopping. Some vendors offer more miles per dollar than others. Those vendors get preference. For example, while shopping for a portable barbecue grill for a gift, The Home Depot was offering 1 mile/dollar while Lowe’s bumped up their reward to 5 miles/dollar. With the grill, boxes for wrapping, and other items, we easily earned 1000 miles. A visit to two other stores and some lunch yielded another thousand miles. This is on top of the AMEX Membership Rewards points earned.
After this experience, it is easy to recommend the United MileagePlus X app to do your shopping. Some purchases may not yield many miles on their own. However, after a few days, weeks, or months, those points add up. Before you know it, you’ll have a free flight or two in the bank.
12/20/2017 UPDATE
There is an added perk to shopping with gift cards purchased through the United MileagePlus X app with the AMEX Platinum card. In my last statement, the purchases coded as airline purchases. This triggered 5X Membership Rewards points. After some thought, it makes sense. While buying gift cards is not airfare, it does produce airline miles like a booked flight would. That's my logic and I'm sticking to it. This discovery is great news. It means that those few vendors offering 5 miles per dollar on their gift cards are also yielding 5 points per dollar on my charge card. It also makes vendors like Walmart and Amazon, which only offer half a mile per dollar, less of a bummer.