I say those horses are the perfect size for you, but I'm a bit biased. I'm the same height/weight as you and bought my own horse last year after leasing many horses of different sizes for a few years before. The last horse I leased was 16.2 or 16.3 and he was too big for me- I hated the way I looked in pictures, and I always had to fight to keep my leg in the right position.
When I went horse shopping I specifically looked for a horse right around 15hh, which is what I got.
Don't worry about other people "moving up" to bigger horses. Bigger is not better or more advanced; it's just a personal preference.