I live in Letchworth but I know Hitchin really well too. We don’t have a cobbled market or Waitrose but we do have a load of amenities (Standalone Farm, the Greenway, outdoor pool, Lavender fields, paddling pool, deco cinema, restaurants, good bars, great cafes), plus the houses are often really pretty, we have lots of trees and green spaces and we have no traffic problems unlike Hitchin.
There is a rough area of Hitchin I stay well away from, whereas the Jackmans estate is set apart, has never worried me and contains plenty of normal people!
If secondary is a concern Highfield seems to be doing pretty well and has a new headteacher or your child may get into the Hitchin schools or Knights Templar, although
getting there will cost your child in travel time of course. Primaries vary though I mostly hear very good things these days.
Letchworth is a commuter town too so the London trains get pretty busy (Well they used to, but unlike living in Hitchin - you will almost always get a seat). Cambridge is also close by of course for shopping, museums etc.
For a million you can get a stunning house and maybe even a historical one, a great garden and space around you to breathe.
I’m biased but I wouldn’t live anywhere else!