I am biased, and I don't wish to offend anyone in south Essex but North Essex is SOOOO much nicer imho. It is a really lovely county with some beautiful and very civilized towns and villages, but like anywhere you have to pick carefully. There are some very nice parts in south Essex but overall it is not great, whereas I think north Essex is the other way around.
Colchester town centre itself has gone downhill in the last couple of years tbh, and has become rougher and more dangerous without a doubt, but I think that is the case for everywhere within striking distance of London. However the demographic in Colchester is extremely mixed, from real old money, landed horsey types, affluent commuters, average middle income people, the roughest of the rough yokels who look a bit inbred and some more recent London 'overspill'.
Lexden is the lovely 'town' part of Colchester but it is expensive.
Up by north station, Braiswick and West Bergholt are really lovely and still easily accessible for town. Village-wise you can take your pick of beautiful places but be prepared to do lots of country lane driving.
Coggeshall is beautiful. Kelvedon also lovely, more accessible but busier due to proximity to A12.
I find Chelmsford is more middle of the road, the differences between rich and poor are not quite so acute or obvious. ahtough it's been a while since I've lived there so perhaps it's changed.
Do you want village or town?
Again loads of lovely villages to pick from but the lovely ones are really pricey. If you want somewhere safe, quiet, pleasant, good schools, accessible for road/train and nice, normal, family orientated people you can do a lot worse than look at places like Hatfield Peverel.