There is no separate bidding for link units and ad units, so now what you're getting in the ad units and the same will be on link units..
You don't get paid anything for the first click on a link unit. Google shows a list of ads to the user, and only pay you if the user clicks on one of those links. So users have to click twice before you get any credit. The CPC for those links should be the same, though the average may be lower because more of them are listed than on an ordinary webpage. Still, no reason to not use them... you can have a link unit as well as your 3 ad units. Cryo.