It is nothing to really worry about. If you have more than one AP, it could be that one client is trying to or is associated to one AP and the other client is associated to a different AP. Unless you are right next to the AP and this is not 100%, then you will see full bars or signal. The client devices are the ones that decide what they can connect at.... they determine what modulation is usable without excessive errors. this is why you might see 54mbps connection on one and 36 or 48mbps connection on another. As long as the devices connect and work fine, I wouldn't pay attention too much with that. I run wirless at home and I get different reading from different laptops but no issues.