They are about equal, I'd say. Roddick reached more finals, but he's older. Both Murray and Roddick had their tennis careers crushed by Federer. He literally ripped out their hearts and squeezed them till they stopped beating. The feeling of utter hopelessness and despair on Roddick's face at Wimbledon 2009 presentation and Murray's tears at AO is a testament to that.
You make a great comparison. I applaud you for that. But there's only 1 major difference. Andy Murray is MUCH MUCH younger. While he was demoralized for the rest of 2010 after the Federer defeat. He can always come back with a positive note, simply because Murray knows, he's got another 10 years left in his career. While Roddick probably tops has 3-4 years left in his tank. So with Roddick, his time is almost over. At the most he can probably pick up 1 slam if he's lucky. He should have picked it up at the Wimbledon but his terrible return serve % was what prevented him as always, even in the dying points.
Honestly, I think as overwhelming as Federer is to Djokovic or Murray and others. I think they still won't give up their beliefs to defeat them. Murray knows, if he can get a solid forehand, Federer is dead. His backhand is an ultimate weapon against Federer, but the forehand screws up all the opportunities. So if he can get that in line, he can hammer away at Federer's backhand, much like Djokovic and Nadal.
But, even if Murray defeats Federer in the tournament, the most important thing is, if he can defeat him and Nadal or Djokovic at the tournament to win a GS. Not just 1, and lose to another in the F or SF.
Back to the topic. I think, had Roddick not won the 2003, he'd get some runners up or SF maybe, but I don't think he'd win a slam. It was Federer that was the wall in front of Andy in all his runs. Occasionally, the regular competition like Hewitt and Safin.