Performance - Competitive
For a competitive comparison, I pulled the WES610N, WET610N and D-Link DAP-1522 into Performance tables for each band in Figures 11 and 12. You can't really make an apples-to-apples comparison among the three since each was tested using different methods. But I figure you're going to do it anyway, so I might as well beat you to it.
The WES610N and WET610N generally are similar in performance, with the main difference being higher throughput for the WES610N in Location F. Looking back over the WRT400N results, however, part of the WET610N's lower throughput could be due to the WRT400N's lower throughput in Locations E and F.
Figure 11: Cisco WES610N wireless performance comparison - 2.4 GHz
But looking back at the internal photos, the WES' use of three formed-metal antennas vs. the WET's two simpler metal + one printed circuit antenna could also be contributing to the WES' better low-signal performance. Unfortunately, the difference doesn't result in any better luck for the WES to reach into my most difficult test locations E and F in 5 GHz.
Figure 12: Cisco WES610N wireless performance comparison - 5 GHz
Note that the DAP-1522 produces higher throughput with a strong signal in both 2.4 and 5 GHz bands when in 40 MHz bandwidth mode.
The WES610N will be a popular dual-band 802.11a/b/g/n bridge for those who want more than one port, one box and don't mind paying a premium price.
For the more price conscious who don't mind adding a switch for port expansion, an excellent option would be a refurb'd WET610N direct from Cisco for $55 with free shipping plus a cheapo 5 port 10/100 switch. I found a D-Link DES-1105 on Amazon from a couple of storefront vendors for around $12 including shipping. But there are plenty of other options under $15 out there, too.
On the other hand, D-Link's DAP-1522 includes a four port Gigabit switch, sells for about half the WES610N and can also be used as an access point, if you can live with its lower throughput with weaker signals.