could you edit the post ?
Add Unix/Oracle and Unix/UDB - after all, they are important platforms for the big customers.
Lastly, the REAL answer is "whatever you're comfortable with". If you're a Microsoft shop with SQL Server experience, then thats the right choice for you. If you're used to the AS/400 - then thats the right choice. I personally would NEVER try to sell an AS/400 to a customer that has tons of Unix/Oracle experience already !
"whats your favourite platform" might be a better poll for the CNC guys !!! Of course, I can instantly tell you what it'll likely be like - 50% love AS/400, 40% love Microsoft and 10% love Unix variants (thats the rough split on what customers run right now !!!)