I think the small gardens for new build is a perception problem.
For planning principles back to back distances should not be less than 21m, so even for a tightly planned estate, you'd expect most family size homes to have a 10 or 11m deep garden with the width either the same as the house if...
New Build does vary look at;
Is it Breeam Code for Sustainable homes rated (better all round performance than Building Regs)
Quality of doors & windows
Quality of kitchen, sanitary items
Quality of finishes and joinery
Lifetime Homes compliant
As someone said pros: 10 year warranty, modern...