IMHO
I would go with a NEW nitrox coomputer unless you can steal one really cheap on Craigs list.
With the prices so low you can find a computer that will serve you well for years to come as a recreational diver. If you decide to dive nitrox you wont be stuck trying to re-sell your first computer. I like to have manual gauges as well.
As far as which computer to buy, it’s up to what you like and your budget. Check out as many as possible. I like some of the ScubaPro computers because of the SmartTrak software and the fact that with the infrared link you don’t have to pay $100 + for a bastardized USB cable that’s worth $5 to download your dives to PC.