Barth was a horrible exegete. His Romans commentary is Paul Lite. 99% Barth, 1% Paul. Barth was a theologian much more than an exegete.
One thing about Bultmann is that he was very honest, ... . He clearly makes distinctions between what he believes as a "modern" reader of Scripture, and what the writer of the text believed. With Barth, you get his ideas and theology, and these can be brilliant, but there is often a disconnect with the text if you are looking for anything resembling exegesis.
My main point:
I have also recently posted on the relation between Bultmann, exegesis, and ideology.