I have to use both. I have a hard time waking up in the morning, so I keep my phone by my bed as the "first stage" alarm. Sometimes I sleep through it, sometimes I wake up, turn it off, and fall back asleep!
This is where an old fashioned alarm clock comes in handy for me. As my "second stage" alarm, I found a really old fashiond wind up clock. You know, the one with a big hand and a little hand and two bells on top with a hammer that strikes them both. I swear it's the most obnoxious, annoying thing. Well, I put that one in my living room and set it 10 minutes after my "first stage" alarm. It's so loud and annoying that i HAVE to get up and turn it off! And once I'm up, I'm up!