Bonds tops Ichiro, Bernie is far better than either of the guys you'd be dropping (unless you're in a keeper league), and Millwood and El Duque are both risky. Both have excellent potential, but have broken the hearts of fantasy players in the past.
At the moment, I'd say Hernandez and Millwood are about even, with a very slight edge to Millwood, whose curve seems far better than it was last year. It's still too early to tell for sure, however.
I guess it depends on who you have to replace Bernie. If you wouldn't be losing too much there, it might be worth it, but if you'd be stuck with a scrub, stay away.
What's your league format? Roto? How many teams?