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It's entirely subjective and totally personal so you can't really make blanket claims like that.
My neighbour just got a loft company in and they did an awful job, total shit show, I'd burn it down and start again, but, he was happy as he only did it to get extra money from the house when he sold.
Not saying you cant get a good job with just a loft company, but it all depends on what you want.
Based on working with a couple companies experienced in it.