You will likely be OK with a regular analog scanner. You will need PL/DPL at the very minimum. Due to narrow banding there are frequencies that will receive two different zones. For example South PD 472.575 and East PD 472.5875. Using PL will enable you to hear only one user, and perhaps the zone you want to hear without hearing the other.
The county was requesting that all radios be P25 capable. I would not count on the switch to digital will be happening any time soon. They are still working on getting all zones to UHF. I would think that the eventual move to digital would be years down the line.
If you are close to Westmoreland county you will need a digital scanner to listen to them.
There is very little to listen to that is trunked. Pittsburgh DPW, animal control, and Heinz Field are trunked. The University of Pittsburgh, USAir, and Allegheny county jail are also trunked.
Decide what you want to listen to. If interested in only listening to public safety, a basic scanner with PL/DPL will work. If you want trunked capability then get a trunked scanner. The benefit is that you usually gain text tags, which is number two on my must have list. This is the next step up in radios, and I guess you could say middle of the road radio.
If you are looking to scan more, then a digital radio would be the way to go, especially if you may use it in other locations, as digital and trunking is used more in other areas. Be advised that most of the newer digital radios have a STEEP learning curve, and may lead to frustration. I don't think digital will be required for quite some time, and by then a newer digital model will be out, and likely have new features. If you are looking for long term, more than 5 years, then digital may be what you want. I personally would only consider the digital radios, but its not what everybody needs.
Consider what the needs are and choose what serves what you need.