Pujols has more credibility. Clark has a curious history; excerpts from google search results (links follow):
Former professional baseball slugger Jack Clark was driven into bankruptcy in 1992 by his appetite for luxury cars. According to his bankruptcy filing, he owned 18 luxury automobiles, including a $700,000 Ferrari and a Rolls Royce. Clark was trying to pay 17 car notes simultaneously, and whenever he got bored with a car he would get rid of it and just buy another one.
In San Diego he is remembered more for his well-publicized rift with batting champion Tony Gwynn,
Clark said, “Trust me, from [a former player], I have a lot of insight into who did what and when but I’m not even going to talk about it. It really doesn’t matter.”
These days former Cardinals slugger Jack Clark is perhaps best known for labeling Mark McGwire a “fake, phony, cheater,” AFTER McGwire admitted being juiced.
The Los Angeles Dodgers fired hitting coach Jack Clark in an effort to get more out of their ineffective offense.
Jack Clark accuses former Dodger Shawn Green of PED use.
When he coached the Dodgers, Jack Clark always wore a jacket. He was the only one on the team who never took his off, because it covered his name and his number 22 on the back of his Los Angeles jersey. “I’m not a Dodger and I felt really weird wearing that uniform,” said Clark. “I didn’t like it because I’m loyal that way, but when I called, I was turned down by the Giants and the Cardinals.’
http://www.nytimes.com/1992/08/08/sports/sports-people-baseball-jack-clark-files-for-bankruptcy.html
http://community.seattletimes.nwsource.com/archive/?date=19970511&slug=2538502
http://blogs.riverfronttimes.com/dailyrft/2010/03/jack_clark_financial_ruin.php
http://www.giantsbook.com/excerpts_jackclark.shtml
All I know as a former ballplayer is that Jack Clark had a perfect baseball swing, and Pujols has a typical juicers swing. The no stride all upper body swing is the first clue on who the juicers are. I will one up Clark. A very high up Yankee official told me that a certain reliever about to retire was suspected to be a steroid user from the time they brought him up from the minors. The same guy later told me that David Wright could only get the bat speed he generated with a little help from PEDs. Another good story, a friend of mine worked in the Mets organization for Steve Phillips, who is now on Sat radio. After Piazza did not get into HOF, Phillips blasted everyone who implied that Piazza was a juicer. Anyhow, my friend told me back when Piazza was on the Mets that he was without a doubt a heavy juicer. His source, Steve Phillips.