[phonebanshee]

I use both. xargs does a simple job reasonably well; if I'm just typing on the command line it often is the tool I use. parallel has many, many more options and ways to turn output from script A into parallel invocations of script B in multiple machines. Parallel is also handy just for parsing filenames; it's become my default tool for manipulating a stream of filenames and then running commands on them. The parallel part is just a nice plus.