In past few years SAP with DB2 implementations has grownup not just because of it’s performance, low storage requirement or low TCO but bundling DB2 with SAP License.
Increase in same platform implementations tends to increase same skill sets and hence reduces total cost of implementation with timeliness. This phenomena has increased number of SAP ECC implementations in SMB market.
With my broad experience in SMB market I have observed many companies implement x86 hardware architecture and always get delay in decision of operating system. Ofcourse their first preference is Widows due to it appears easy to administrate using GUI, where infact troubleshooting on windows is really tricky and difficult (No Offense!). I personally prefers SLES due to it’s SAP optimized operating system and integrated support with SAP, but no doubt RHEL is also good and stable operating system with SAP environment.
If SAP manages to include any of this Linux OS in bundle with SAP & DB2 license then, it will be more cost effective solution for SMB market.