It is very important to understand that when doing interval training, the big portion of your calorie burn will occur after the workout is over. Don't hook yourself up to a monitor, observe that you burn more during steady state than interval and therefore dismiss interval training all together.
I like both! The more variety and the more you mix it up...suprise the body...the BETTER!
Again, Interval training should be done only a few times a week. If done correctly, that will be plenty!