It's more likely the phone is trying to establish a connection first on one and then on the other and not getting it on either.
The phone will try to access via
EV-DO and then go to a 1X connection. Because you make numerous connections in a normal page load (for various content) it can seem like it's "fighting" over it.
I'm not convinced going to 1x saves all that much battery power, but I'm in an area where
EV-DO is just about everywhere.