i'm a fellow newbie to diving and i tell ya, better go to the store to look at the watches.
1. the buttons used to navigate the settings, one or two or more? easy to navigate through the settings?
2. preferred size of dive com. suunto zoop has a big face, so does the cressi leonardo/giotto. or do u prefer a 'watch' size face like the suunto D4i or D6?
3. are you a guy or girl? if u have very small wrist, you'll notice you need to put to the last few holes of the watch, leaving a very long strap dangling. this is common for zoop/leonardo. u can find fellow divers to see which watches can change strap. D4i/D6 its a 'watch' u can wear daily the straps are like watches.
4. do you want a watch with Hot swap battery or non-hot swap battery? as in, able to change battery on your own like oceanic geo? cos suunto not all have swapable batteries, have to bring to retailer to do.
5. do you want to be able to upload the dive log to your computer? some of the watches have this function, buy the usb cable e.g. d4i/d6
6. Nitrox/Air/Gauge/freedive modes. most dive comps now have nitrox & air modes. you may want to consider gauge mode. this is for situations where you want to follow your own dive plan, don't want to use the dive comp cos its too conservative and it'll beep like mad when you exceed their recommended dive time, depth and so u turn on gauge mode to only use the watch to measure depth and timer.
7. does the dive comp have a easy to turn on 'light' for when u're doing night dives and want to check the depth, don't need to shine the torch on it (i am not sure if all dive comps have this)
i like this site for the reviews. http://www.dive-computer-wizard.com/