I used the bcm5700 driver for a Broadcom Corporation NetXtreme BCM5703X Gigabit Ethernet (rev 02) onboard a HP Proliant server.

Like this, I had trouble with UDP protocols:
DHCP reply took a long time, trouble with NFS (UDP), TFTP for PXE boot did not work at all.

I did not try the tg3 driver. So, I only can say that this card does not work properly with the bcm5700 driver.

My Dell Poweredge server shipped with an onboard Broadcom NIC which I believe is a 5700 type. Every time the system booted up, it got hung up waiting for the NIC, then gave up and failed to initialize the interface at all. YAST listed the NIC as "ATA" and said it was configured with DHCP, neither of which was correct. A simple "ifconfig" only listed loopback interface and no amount of fiddling with the bcm5700 driver module on the install CD would get the Kernel to recognize the eth0 interface.

In the end, my only option was to try another distro, so I installed Fedora Core 4 and the card was recognized and configured immediately without any problems.

These cards are often found in modern servers.
They work great out of the box with the tg3 module.

Only if you want to use teaming mode or VLAN on the more sophisticated (dual port) models, the proprietary bcm5700 driver is required; this one is a bit fiddly but works also great.