A switch is better than a hub. Hubs split the bandwidth across all ports, so you'd get lower performance.
You can think of a client-bridge router as a wireless switch.

Can I use an old router (Linksys WRT54G Wireless-G Router) as a switch or a hub?
Yes, you can use it as a switch. If you disable the wireless AP and DHCP, then it's basically a wired switch.
http://www.ezlan.net/router_AP.html

I don't think the WRT54G had client-bridge mode by default. You'd need to flash it with a third party firmware like DDWRT or Tomato. You need to look at the exact version. I think there were at least 8 different versions.

Not sure what you mean about security. Switches don't control security. As for wireless, that's controlled by the primary router, not the client-bridges.