Which is better Cardio

I have some friends that one set goes bike riding and the other goes roller blading. Both say one is better then the other. I have been thinking of taking up one of them becuase the cardio on the old machine is getting boring.
Which do you think gives you better Cardio work out?

intensity and duration are the things to keep in mind. but, the key thing to do is to break up the same ole routine. when cardio gets boring, we just dont do it.switch it up, i feel both are good forms of cardio.

Id say roller blading... unless you mean doing tricks and stuff included. Although bike riding is more easier if you plan on going long distance or on certain roads. Only reason i said roller blades was trying to imagine the burn it would give trying to get up a hill in them

Well, I would say roller blading, but bike riding is a great work-out as well, I prefer a bike over roller blades.

If you want to burn it faster sprint like a psycho and keep your heart rate up.

Well I went and bought myself some roller blades.... after my nine hunderth fall on my a$$ I decided maybe there not a good idea. Now I am not the type of person that gives up easy, but after having the neighborhood come out just to watch to see which way I fall .... I decided to trade the suckers in and now I have myself a really nice bike.... so far no crashes with the bike, but just wait I am sure it will happen here pretty soon....