In all honesty with T-mobile in my office I was lucky to get 1 bar with my N4, I now get 3... My wifi is just as good if not better than my N4.
Some phones report more signal than they actually have, the algorithm to show the bars is different. This was notorious with sprint and HTC, showing 3G full bars when you would have nearly zero signal. The N5 with no carrier modifications to make them look better will display your true signal. The best way to check if your signal is actually weaker is to use an app the will tell the full dB of the signal.
Rootmetrics is a good app for this ( may be called "cell phone coverage map" in the play store.)