DB2 for Windows and DB2 for Linux use the same code base. So there is no functional difference for applications running against either system. DB2 is equally stable on both platforms - platform stability is a different issue outside the scope of IBM, of course. Likewise, DB2 takes advantage of the respective kernel's feature wherever possible. If one kernel has features that the other does not, this can/will lead to differing performance. The only reasonable statement you can expect here is to install DB2 on both systems, apply respective tuning and then measure performance differences. And at the very end, it comes down to the skills you have available in your shop. If all you ever did was Windows and you have no Linux skills, then such a migration will be troublesome.