Welcome to the forum.
The advantage of buying an existing house is that you can see what you are buying, have a full survey done before exchanging contracts so you know in advance if there are any issues and can lower your offer to reflect them and you can see what the neighbourhood is like.
With a new house you cannot do any of these things.
More importantly, 99% of those buying new homes report defects to their housebuilder in a matter of weeks 42% more than ten defects. Most housebuilders are not very pro active in sorting the defects out!
The NHBC spend around £90million fixing serious defects in around 11,000 new homes each year.
Whether you buy one of these is a lottery.
Buy what you can actually see and survey and pay the right fair market price.
That's not going to be a new build home!