Warren is very Pro-Israel, much more than Cory Booker.
What in the world makes you think that? (That is, assuming that by "Pro-Israel" you're talking about siding more with Israel over the Palestinians.) Like I said upthread, Warren's past comments on Israel, before she started to drift in a more dovish direction, were just the same sort of boilerplate comments that ~95% of US Senators would make whenever asked about the issue.
I went point by point in my earlier post on examples where Booker has been more hawkish than Warren on Israel, and what is the response to that? "Warren is secretly even more hawkish on the issue than Booker is, trust me?" 
Warren's vote for the Iran Deal was expected.
Booker's vote for the Iran Deal was a massive betrayal to Pro-Israel voters and Pro-Israel Jews.
Many of us in the Pro-Israel community, GOP and Dem, supported him his entire political career and he wouldn't even give his constituents a real chance to talk to him about the negative effects of the Deal after he supported it.
He had deep personal and emotional ties to Jewish communities. He was the President of a Jewish organization in college and had cultivated those relationships for many years.
Warren met with her constituents, before and after supporting the deal, and cares about what they think, even if she voted against how they wanted her too. It's easier to respect someone if they do something out of principle than if they did it out of political opportunism.
Also, I have friends who know Warren personally and they believe she's one of the biggest supporters of Israel on the left. These people have been very involved in the Jewish community and I have no reason to doubt them.
Maybe I, and many other Pro-Israel activists, are being irrational but it's harder to forgive a longtime ally for a massive ideological betrayal than someone who is relatively new to the scene.
That being said, I wouldn't support either over a republican.
