This is part of a larger project reviewing commentaries on each book of the Bible. Follow the links from that post for more information on the series, including explanations of what I mean by some of the terms and abbreviations in this post.
I have a hard time deciding between Thomas Schreiner's NAC (2003) and Karen Jobes's BECNT (2005) as my first choice on I Peter. I think Schreiner's is the best NT volume in the NAC series. Jobes has a good deal more space in her commentary, and it's a little more recent and thus has an edge in terms of having more scholarship to interact with. Schreiner includes II Peter and Jude and thus is more limited in scope in his I Peter portion. Both seem to me to be excellent both in exegesis and in sorting through the contemporary scholarship, but Jobes has more space to interact with other scholars. Both are well-written and easy to read, although Schreiner will be slightly more easy-going for those without Greek. Jobes comments directly on the Greek text, although she transliterates and translates every time she gives an expression in the Greek. Schreiner works in transliteration and translation entirely.
Both come from a theologically Reformed background, but Schreiner presses those issues a little more firmly (not a bad thing, as far as I'm concerned, and I don't think he goes overboard as some do). He connects his comments up with broader, systematic theology categories. I count both as theological conservatives, even on less central matters such as gender issues (both are complementarians, although Jobes doesn't think I Peter itself deals with the general issue of male headship in marriage, as she thinks Ephesians and Colossians do, but rather just deals with women submitting to unbelieving husbands for the sake of evangelism).
When I let a friend borrow some of my commentaries for a sermon on I Peter, he told me Schreiner's was the most useful of the bunch and an enjoyable commentary to read, although several others were helpful to him. He didn't get to read Jobes, however, so I'm not sure how he'd compare the two. On Schreiner, see also Craig Blomberg's review. Surprisingly to me (given how much I like Blomberg), I think I agree with Schreiner in most of the places Blomberg takes issue with him.
Jobes contributes three things in her work that are worth mentioning. First, her treatment of the Old Testament in this letter spends a good more time than usual in looking at how the fact that OT quotations are from the LXX should affect how we interpret their use here. This is a welcome feature that I think will affect future I Peter scholarship will have to take into account.