Most effective dual-airport extreme setup?

I have 2 airport extremes (prev gen -- non 802.11n) in the same household. One on each level. They are acting as separate WAP's, not as routers/DHCP.

Basically I have 2 SSID's: upstairs and downstairs.

Is that more effective than running 1 SSID using WDS? I heard that WDS will lower speeds, etc. Wouldn't it just be better to use two diff SSID's and have the OS on the client decide which has a better signal?

Thanks

Here is my setup:

The verizon FIOS is acting as DHCP... all of the other switches are Cisco gigabit unmanaged switches.