I was chatting to a recruitment consultant a while back (we were hiring rather than my looking) and they were saying that something like 90% of people who accep

I was chatting to a recruitment consultant a while back (we were hiring rather than my looking) and they were saying that something like 90% of people who accept a counter offer leave within a year. If you're unhappy somewhere unless money is the reason you're unhappy, a counter offer (assuming as most are it's just financial) isn't going to change that. The only way you should consider a counter offer is if it really addresses the reasons you're looking to leave and you really believe that they'll deliver on it.