http://journal.dedasys.com/2008/11/24/slicehost-vs-linode
I was with SH myself, and before I wrote that article, I dropped them an email asking about the 64 vs 32 bit thing, and was simply informed that they have no plans for 32 bit, so I went ahead and switched, then wrote my article and have been happy since. I sincerely hope the SH guys will get competitive again, at which point I'll gladly update my article.
Also, something that Linode was missing for a while was backups. They're rolling them out now:
http://blog.linode.com/2009/04/03/backup-service-enters-beta...