If I am not mistaken, most thieves use a meba for 10 levels, until level 35, where they get a new claw. The reason for using the meba for so long is that it has a "faster" throwing speed. I am not positive about this fact.
But I'd say that go ahead an upgrade, it would help to have a higher attack than your current claw. I am not sure on the attack difference though. I guess if you don't have the money or ores, then you should stick with your current claw.