I mean if you think about it, you're looking at ~$75 for the Xk3y and ~$70 for a hard drive, then that's it provided you have someone dump your keys and you do the Xk3y install yourself.
Burning/flashing, ~$25 for a compatible burner and ~$50/50pk for the DVDs. I've had one burner crap out on me for some reason, and the DVDs I usually burn with about 75% success rate, so I waste about a quarter of a pack on bad burns. Plus burning takes forever.
I've done both, I know the ins and outs of both, they're both viable options but I'd definitely say the Xk3y is worth it more if you plan to use it a _lot_. If not that much, maybe only once in a while, probably a flashed drive is the way to go.