I've been reading up on HIIT (high intensity interval training), and I was just wondering, which is the better choice? A treadmill or a jump rope? The only thing I'm worrying about for the treadmill is that it takes time for the speed increases/decreases, which might disrupt the workout, right? Also, for whichever one is better, what's the best interval/speeds to do it on?
Thanks!

PS. Will doing HIIT make my body buff?

I'm looking to slim down and get a leaner/more toned body, and I definitely don't want to have a buff body since I'm a girl.
running outside on a track or just on a field is best. non-treadmill running is better than a treadmill or jumping rope. intervals of 15:45 seconds would be a good start. the best speed? that would have to be your fastest running pace. that's why it's easier to just run outside or on a track. no you won't get buff, since you do not have the hormones to get buff.
although if you can only run on a treadmill or jump rope, i'd go with jumping rope since it uses more muscles. not to mention there's that slow-down period on the treadmill which makes it hard to time.