Recently, I posted a blog entry where I described that "Not All GigE Are Equal", strongly advocating the use of Broadcom GigE devices when faced with a choice.
However, after spending time in the code, I've discovered that there is quite a range of differences amongst Broadcom gigE devices.
I had considered listing a full table of them, but it seems that would be a bit onerous. Take a look at usr/src/uts/common/io/bge/bge_chip2.c if you want to find out the gory details. But in the mean time, here are my recommendations:
If you have PCI or PCI-X: Choose a bcm5704 if you can. It has pretty much full feature support, but you need to pick a recent revision (newer than A0.) Look for pci ids of pci14e4,1646, pci14e4,16a8, or pci14e4,1649. These chips alls support PCI-X, multiple rings, full checksum offload, and multiple hardware tx and rx rings.
If you have PCIe: As far as I can tell, all of the PCIe chips that are Solaris supported lack support for multiple hardware tx/rx rings. This is really unfortunate, as it will have a negative impact on Crossbow benefits. But apart from that, it looks like the 5714 and 5714 series are your best bet. They both support jumbo frames, and they both have full checksum offload support. Look for pci ids of pci14e4,1668, pci14e4,1669, pci14e4,1678, or pci14e4,1679.
What this really says, is if you have to choose between a PCI-X card and a PCIe card, surprisingly, choose the PCI-X card (if you can get a 5704). Save your PCIe for framebuffers or HBAs. (Or, better, 10G cards like Neptune.)