TC, I live in the Boston area as well (about 15 miles west). I've owned many scanners from many different manufacturers over the years and now I've whittled them down to two: Uniden Homepatrol 1 and Uniden 430HP.
Both of these scanners will pick up about 90% of what you can hear in the Boston area: UHF, VHF, most trunking systems and P25 phase 1. There are relatively few P25 systems in the Boston area right now. From my location I can only pick up Lexington and Waltham P25 frequencies on either scanner.
Supposedly the Worcester State Police are changing over/have changed over to the P25 Phase 2 system. I bought the 436HP to be able to eventually hear these but even though I have the system programmed I've never heard a single call from that system. I might be too far away for it.
The 436HP also lets you hear DMR frequences if you pay an extra $60 for the firmware upgrade. I've done this and I imported a bunch of DMR frequencies from the DMR database at
United States Digital Mobile Radio (DMR) Frequency Search. I can receive calls on Only 6-10 of the hundreds of DMR frequencies (all of them conventional, since I didn't want to futz around with trunking DMR at this point), but it definitely picks them up. A lot of commercial and Spanish-language radio traffic.
I know others like the Whistler scanners, but I stuck with Uniden because I like its programming philosophy and the Uniden Sentinel software for HP-based scanners is very good, and it automatically imports the latest full databases from RR.