The main thing I know about the two towns is that Derry doesn't have its own public HS so all the Derry kids go to Pinkerton Academy. I talked to someone who used to live in Derry, and he had two sons at Pinkerton. His assessment was that it's a great school if you're really smart, or you're really slow. If you're really smart they'll bend over backwards to help you achieve. If you're really slow, they'll literally drag you through to graduation. But if you're average, you get overlooked. He had a really smart son, and a son that on a good day was a B student. This son had a lot more trouble making it. I think the school was just too big. He needed tutoring in Chem, but it took two weeks to determine that they didn't have enough tutors to spare. Recently this gentleman has moved to Bow, where the school is a fraction of the size, and his son is getting what he needs.
Now Londonderry is supposed to be a top notch district. The music program at the HS (something I always look at
) seems not only comprehensive in scope but stellar in quality. They also have a district preschool that mixes average children with those that have special needs, something we were looking at closely when we first moved to NH. It's too bad we didn't find a house in Londonderry, because I felt a little more confidence about it's school system being more established. The other thing is that Londonderry was a little farther south on the 93, so it would've been a shorter (or more direct) drive to family in MA.
One downside to Londonderry is that it doesn't have public playgrounds. I believe it was Valerie C who told me this, but hopefully she will see this thread and elaborate a bit more. We do occasionally go there to go to Discovery Stop, an indoor playground/play facility for young kids. It's a fantastic place, and great for a rainy/snowy day.
We looked at houses in Bedford and Londonderry, and the prices for what you could get seemed to be about the same. Bow was more expensive. But I would think that's a bit too far north for you.