Well the Commander Nitrox was an e-bay item and was 3yrs old. I was told it only had 42 dives on it and it was in perfect working condition and the pictures showed it was perfect on the outside and included the anylyst sofware and cables for $300. The downside there was that Cochran will not work on these anymore if it goes sour and I thought about what Mark said and it sounded like good advice. It's a great computer but not repairable, all Cochran said they would be able to do was check it and clear the memory and if there was anything wrong I would be able to upgrade at a discounted cost to the new Commander.
The Vyper and Pro Ultra are also excellent computers and I thought about equally matched. There are some differences that to me were not important such as 24 hr lock out of the Pro if violations are ignored. I don't paln to ignore any violation unless I'm seriously in trouble and then I would not be diving for 24 hrs anyway. Gauge mode I didn't find a need for it with the diving I do and if I ever need it, I have a bottom timer and analog gauges anyway. The other differences were temp display on the Vyper and watch mode, for me also not real important. What really closed the sale on the Pro Ultra was the display. It was a bit bigger, better layout and easier to read in my opinion and I was not crazy about the graphs on the sides of the Vyper. I just preferred the numerical readings of the Pro Ultra. Like I said both are great computers and time tested to be very reliable. I read both online manuals for them read reviews and read plenty of comments about them on this board. Also the difference between a memo mouse or a cable was not a big deal either. For me it was just a matter of personal preferrences that made the difference between the two since the price was the same $299.