Can only use 1 NIC at a time, so if you wanted to switch between you'd have to re-establish the connection. Have you considered maybe Home Plugs as an option? you plug in one end into a router, the other into a power source then the 2nd one into a power source and into your PS3. It acts closer to a wired connection.
Or if you really needed to switch between the connections Wireless (Gaming, downloads, etc) and Wired (LAN with a router and your PC). It's a hassle but it will at least give you a better stream.
Core2Duo E8400 (@ 3.0), 8gigs of Mushkin, Vista Home Premium SP2 64bit, 2.5 TB of Space, Wired to Linksys WRT54G wired to 80GB MGS4 PS3 on Sharp 32" 720p LCD TV