I'm not crazy about SexyBookmarks - had issue getting it to work properly with my custom post types, and I've never liked AddThis because it opens up a popup that's sometimes hard to get rid of. It kind of depends what you want and where you want it.
For facebook likes and tweets, on some sites I just add the custom functions for these, and on others I use a plugin called ShareThis. I like the way the buttons look better than the SexyBookmarks.
I also use the WP-OGP plugin to get the Open Graph data into the header on each page.
The +1 button - where I've implemented, I again added it to the custom functions file (using either Thesis or Genesis WP frameworks)
As far as general social media buttons (just the ones that point to your twitter account, linked in account or facebook page) I like the Social Profiles Widget for the sidebar. Nice clean icons; easy to place and implement.