I have an old cobra and I have a escort 8500x50, both have saved my ass multiple times, enough to pay for themselves many times over.
The escort definitely has a much longer range, but I doubt there was a question about that.
I've been ticketless for 3+ years now, knock on wood, I'm that lucky SOB who gets hit with a laser through another cars windshield. Happened twice in one weekend actually by cleverly hidden motorcycle cops.
I really think you'll be well off with the escort 8500 or up, the V1, or the Bel that anthony recommended.