I can tell you about the 100-400 IS lens, the slide zoom is excellent it took getting used to but it is fast and easy to control plus you can lock the zoom at at any point. If you need more than the 200mm offers and have to resort to a 2x converter I would suggest getting the 100-400 in the first place. I have used the 2x type ll converter it's really good for whit it is but it is not a replacement for a good lens in the first place. Randy