I think Readington gets a little more urban spillover from Somerset County and is not as "country" as Raritan Township. I also think that Flemington is a great place to live if you like a small town location- its vibrant, busy, low in crime, and the housing stock is gorgeous. And there is a Tractor Supply Company and a dog park in Raritan Township
On the downside, Raritan Township is quite expensive and has very high taxes, even by Hunterdon County standards. Friends I have that live in the township pay over $14k a year for a 4 bed, 2 bath home on one acre lot. Traffic on the Route 202/31 circle is atrocious during rush hour and on weekends (the Dvoor circle is still good).