From someone who lives in Worcester county… the answer is Worcester county. There is a clear feeling of entering “Western MA” as soon as you pass Athol on Route 2. Also, towns like Holden, Rutland, and cities like Fitchburg and Gardner are west of the city of Worcester, but if you ask literally anyone who lives in those places if they think they live on western MA, they would say no, definitely not. I live in Fitchburg. I do not live in Western MA. It still takes me less than an hour to get to Boston, and twenty minutes to get to Worcester for Pete’s sake. Western MA is very sparse and rural, with the Quabbin area, the Pioneer Valley, and the Berkshires. That’s it. Worcester County is central MA, not western MA, and there is a difference.