Wat? other than the arguably weak first arc of Sam Wilson, both books are great, The Sam Wilson series goes into the downside of being Captain America, everyone expects you to agree with them, he is likely the biggest victim of the news in the marvel universe, almost Spider-man-ish in a way. Steve Roger's series is basicly a in-universe what-if, Spencer's writing had me on the edge of my seat anticipating what would happen.
I would argue that, given enough time, Spencer's Captain America run could overshadow Brubaker's run. Though I would have to read through Brubaker's run all the way through instead of the snippets I have read.