The amount of bars doesn't mean anything so you can't go by that. You need to check the actual signal strength under settings -> about phone -> status.
I primarily keep my Gnex in 3G mode for battery life reasons...last night, I had my wife's Droid 3 in one hand and my GNex in the other.
My wife's D3 was bouncing between -94 and -95 dbm's but showing full bars.
My Gnex was showing a solid -93 dBm but only showing 2 bars.
My Gnex was getting a better signal despite the fact the number of bars were less. The amount of bars shown based on signal strength is at the discretion of the manufacturer. Obviously, Moto's definition of excellent reception is different than Samsung's.
So you can really gauge by simply looking at the number of bars.