I have found that the 'soldering', if you wish to dignify it with that word, on the Bachmann DCC Equipped locos is less than stellar. If I were going to purchase the Bachmann 70 ton DCC Equipped loco, I would also purchase a Digitrax DZ123 decoder and install it.
They are small, but work well. Make sure you check the stall current on the Bachmann loco first. I replaced a Bachmann decoder in an 0-6-0 with one of these and it runs great! Of course I also added pickups to the tender wheels.