I have lived in our new build for 14 years. Lots of advantages as people have highlighted - very low maintenance and upkeep costs.
Disadvantages:
Parking! Check it out. Parking is a nightmare and when I tried to sell a few years ago buyers wanted to come at weekends when it's at its busiest and couldn't park to view the house. Check how much you have.
Small postage size garden
Flats built on estate - flats mean lots of traffic, parties, noise... Check if estate has them
Resell value - it's taken many years to increase in value in line with equivalent older properties. An estate agent said it takes about 10 + years to settle. That's because people don't want to buy a nearly new 'new build' when they can customise and live in a brand new house for a similar price
Social housing. My sister lived on an estate where private and social was mixed. Worked well. On my estate it's all private at the front and social housing at the back. Really segregated and there have been problems with social housing tenants. I think it would have been a lot less if we weren't so separate - very them and us.
Check space - mine is actually really spacious. However, showrooms use lots of mirrors and beds and sofas that are smaller than the standard size.
Difficult to extend if small garden.
From what you say I think a new build may be perfect for you - just take into account the above. I dont regret buying ours but I would have bought the house next door that has better parking had I thought about it more