My experience with HW's is that they're excellent guns, but all of mine have needed a little work right out of the box. Once that work is done though, they're top notch. My HW30 had a bad piston seal, my HW95 started grinding during cocking within the first 500 shots and my HW45 wouldn't stop dieseling until I stripped it down and cleaned it out inside.
The Air Arms guns I have owned on the other hand were perfect right out of the box, but my TX200 didn't really measure up to its reputation as a tack driver until I tuned it to 12 fpe. At 17 fpe, it was one of those guns that would shoot mostly decent groups with occasional fliers. I felt disappointed with it because accuracy is the main reason why anyone buys a TX200. Once I installed a 12fpe kit however, it was transformed into the rifle I had hoped for.