To put it in plain talk. Narrowband doesn't have the "oomph" that wideband has when it comes to a scanner. The "window" is much tighter and "seems" weaker for the power being used. But narrowband is the best option right now when it comes to frequency usage. We can add more chans in the VHF and UHF ranges now, and when the next phase of narrowbanding comes into play and the switch to digital (Prefferrably P-25 Phase II TDMA type), there will be an even bigger allocation of available chans.
Here is a poor explanation: "Wideband" VHF High- You have 155.0000 to 155.9950 with a relatively smallish number of usable freqs in that bandwidth. "Narrowband" VHF High- 155.0000 to 155.9975 with many more usable freqs. The next phase tightens that even more, and with the addition of TDMA digital would even double that. (TDMA gives you 2 "Slots" per every freq. So if you take an old school 3 freq repeater set up of say 155.3700, 155.6100, & 158.9700 you had just the 3 chans to run on. With TDMA you would now have 6 chans.) Hopefully the longwinded explanation helps and doesn't confuse you even more.
Admin for AR, IN, LA, MS, and TN
Scanology, its the path to monitoring happiness!
Support your local Scanologists!