Sounds very sensible to me. In the Canon world, I've got the aforementioned ancient version of the Sigma, and it's a really great lens, but I don't like carrying it around all the time. However, I've got a 70-300 IS lens that despite not being quite as sharp, and without the same speed, gets used a lot more because it's easier to carry around. If I were starting from scratch now, I certainly wouldn't have both. There's no point buying more or less lens than you need or can use.