Also I'd be surprised if you can find any 10GBe cards that are better supported in Solaris than Linux.
Solaris has been on a downward trend since they dropped x86 support that time briefly and really I can't see it coming back. I understand why Solaris drivers feel more finished because there are less of them and the ones that actually get into Solaris releases would have passed a lot of QA. However my guess is if you buy hw to run Linux on as carefully as you have to buy hw to run Solaris on, you'll most likely get a lot of parity in the driver support. I know how much work goes into the RHEL ethernet and storage drivers, and from what I can tell this is substatially more than goes into Solaris equivs at this time (5-10 years ago I'd say quite the opposite was true).