That's true for nearly everyone.
But forget about that comparison. I find Adam Schiff to be highly credible in his own right, and I always have. Those who question his credibility do so on 3 claims which I think are completely false: first that he lied about the Russian investigation when he claimed to have proof of collusion. He didn't. The proof he was describing was fully detailed in the Mueller report. Schiff believed that it proved collusion and I agree with him. Mueller did not disagree but stated that he could not reach that conclusion without more evidence. From this slight dispute, Trump supporters here and elsewhere have tried to make the claim ever since that Schiff is dishonest. It's an absurd claim.
Second was Schiff's attempt, a month or so ago, to paraphrase President Trump's July 25th phone call. That was a dumb move on Schiff's part, because the actual call was bad enough and didn't need translation. But it was not at all dishonest, and testimony taken since that time has shown that it was truer than Schiff may have even known at the time.
The third claim showed up only a few days ago: that because members of Schiff's staff know who the Whistleblower is, that means Schiff himself must know, and is therefore lying about it. Beyond the fact that the identity of the Whistleblower is completely irrelevent at this point, this claim is made on specious assumption and without any evidence whatsoever. It is not surprising at all that Schiff would deliberately not know the identity, directing his staff not to tell him. Ben Bradlee, the editor of the Washington Post in the 70s, never knew who Deep Throat was; he instructed Woodward and Bernstein not to tell him.
Schiff is an honest man, nothing like the President, and the attempts to smear him are pathetic and foolish.