That is a really tough choice. Everybody has a preference. And none of them are wrong. I'm the opposite of Scott L. I had a console, went to a wrist and hated it, and am back to a console. Personally I'm really hard on things on my wrist. I tear them up something awful.
In these 2 computers you are really comparing Apples and Broccoli, though. The only real similarity is that they both are good dive computers. The Atom is a smaller, compact wrist-watch style computer. It packs all the features of an Oceanic computer into fairly small case. Its well thought out, with a fairly common sense display and allows you to read up to 3 different transmitters and up to 3 different nitrox mixes. It's a fantastic choice for a worrisome parent or spouse.
The Cobalt is using some newer technology and features amazingly vibrant colors with its OLED screen. It can be viewed easily from almost any angle. It packs a very intuitive digital compass and is one of the easiest to navigate menus designed for scuba computers. Literally laid out like a DVR remote. It also boasts a rechargeable lithium Ion battery that offers pretty good battery life off a single charge and can be recharged through a USB adapter or using the AC Adapter.
As a newer diver, generally speaking my reccomendation would be along everybody else's. Get a more inexpensive computer first. It will do all the things you NEED a computer to do and many of the other features these 2 more expensive ones will do for you. It'll also free up a little bit of money to work towards some of the gear you'll wish you had next, such as a nice regulator, bcd, and/or suit.
