Hello,
Your first question is made more difficult by the fact that some scanners sold by Radio Shack are made by GRE and others (also sold by Radio Shack) are made by Uniden. If you are looking at the Uniden BC92 (or 72) then you should also look at the RS Pro-83. The Pro-83 is also made by Uniden and unlike the BC72 or BC92, has a computer interface. If you are looking for a newer unit that does trunking, then you should be looking at the Pro-97 or the BC246T. The Pro-97 has Mil-Air coverage, which the BC246T does not, but the BC246T has Dynamic memory which the Pro-97 does not. The BC246T has the same form factor as the BC72 and BC92 and the Pro-83. All four of the Unidens mentioned run on 2 AA batteries. The Pro-97 runs on 4 AAs. If you are happy with your Pro-94, I would keep it and also look to see what else is available that would be fun to play with. (The BR330T comes to mind.)
Mark