The highback and flex should still be the same but we changed up the ankle strap and toe cap for 2013. The ankle strap got borrowed from the 390, so it's thicker and super comfortable. It will also provide a bit more support and response, since it's gotten beefed up from the 2012 Mob strap.
If you aren't stoked on the flex of the Mobs, you really can't go wrong with a pair of 390's. They are definitely lighter than Targas, but not as light as Mobs, so they are right in the middle. Honestly your best bet is to find the nearest store and just pick one up and see for yourself. Everyone is going to have a different definition of what "light" means to them.
Hope that helps.