Outside of the design, Under Armour and JBL tuned the Sport Wireless Trains to be more neutral than the Project Rocks, which are quite bass heavy. I was able to notice that right away when I listened to a couple of albums on the Sport Wireless Trains -- the vocals just seemed to pop and be more clear in every track. The other main difference, and this is a big one, is that UA made the Sport Wireless Trains $50 cheaper than the $250 Project Rocks. $200 is a much more compelling price point, especially when it still has all of the features that make The Rock's pair appeal to people who hit the gym frequently.
The Sport Wireless Trains are made from rugged, sweat-resistant materials (IPX4 rating) and come with breathable ear cushions that can be removed and washed -- that's going to make it easy to clean them after your workouts. They also feature 40mm JBL drivers, a 16-hour battery life (5-minute charge will get you one hour of listening), oversized volume and playback buttons, as well as a 3.5mm audio jack in case you don't want to do Bluetooth pairing. Additionally, Under Armour is throwing in a 12-month premium subscription to its Map My Fitness service, which is usually costs $30 per year.
Unfortunately, as with the Project Rocks, there's no active noise-cancelling -- and that's likely going to be a deal-breaker for some people. But if that's something you can live without, the Sport Wireless Train headphones are hitting stores in early August, though you can pre-order on July 24th from the Under Armour and JBL sites.