I also believe that measuring is 'better'
HOWEVER! I like the scale more

With the scale, you get instant feedback and can usually see if you're on track or not. With the tape measure, if you measure every day--or every week--it hardly fluctuates. You really have to do it once a month or once every few months. But the scale you can hop on weekly and instantly see if you're on the right track.
If you said I HAD to get rid of one or the other, I'd choose to keep the scale even though I do believe that the tape measure is a more accurate method.