HIIT question

So, I did some research last week and found out that high intensity interval training (HIIT) is a brilliant way of losing weight and getting your fitness levels up, and then i realised this is what my old gym (when i was 17) told me to do and with them i lost nearly 3 stone. However, the research i've done says brisk walk and then very high/intense running/sprinting in bursts of 30-60 seconds depending on fitness level. Now, my old gym had me on a different one where i would range from 5km/h to 12km/h in bursts of between 2 minutes up to 7 minutes for a maximum of 40 minutes...

so the question is - opinions on which one has the best results? Have any of you had experience with either way? I so far only have my old gyms method to go by, took me 2 years though.