I tend to believe that if being an RN is your goal that it is best to go for it!
My question to you is how much debt are you talking about? You say you won't have to work while in RN school, but then you will be in more debt, is that because the tuition is so much more? Remember that your salary will be a lot higher with an RN than with an LPN, so unless you are talking about a HUGE amount of debt, you will have the salary to pay off that debt. Also, you may even consider a part time job while you do your RN, if you think you can swing it, to offset some of the debt. Personally, I worked full time nights while I was in nursing school, certainly that totally sucked and I wouldn't recommend it, but perhaps doing some part time work would not put too much strain on your study time and ease some of the financial concerns. Just a thought.
The truth is you have 2 good options here. I'm sure you will make whatever decision you make work.