Previous owners of my flat put in a Howdens kitchen in c. 2005 and it still looks serviceable (although we changed the worktop), which is pretty good for the price point. Not sure how the quality has changed in the intervening 15 years though.
Also they don’t change the styles very often so when we wanted to replace a panel 10 years later they had exactly the same design and colour in stock.
Howdens are nearly always rated by the trades.
I think it's to do with space behind the unit for pipe work.
In terms of quality, dunno. Unsure if there's a huge difference at the price point your at. Not bitchy.
A friend is having full custom, I've winced at the prices for a bin being resold by the fitting company he binned.