Although the throughput behavior in the various security modes seemed to improve for both the Belkin and Buffalo Tech cards, the differences were significant enough to not give me a comfortable feeling about the stability of either card's performance. Judge for yourself by looking at Figures 3 - 6 below.

Figure 3: Security mode performance comparison
Buffalo Tech WLI-CB-G54 client - Run 1
(click on the image for a full-sized view)

Figure 4: Security mode performance comparison
Buffalo Tech WLI-CB-G54 client - Run 2
(click on the image for a full-sized view)

Figure 3 shows that in the first run, the combination of WLA2 and Buffalo Tech client produced reductions in average throughput of approximately 8% with WEP128, and 17% with WPA-PSK / TKIP. Average throughput actually increased with WPA-PSK / AES enabled by about 4%, mainly because this mode seemed to eliminate the throughput hopping effect seen in other modes.

The second run shown in Figure 4 produced throughput with less variation in each mode, and more like what I'd expect from previous testing of Broadcom-based products. The main puzzler was the increase in throughput with WEP128 enabled, but I think that's more a function of the normal "hopping" behavior of the Buffalo Tech client.