Hello everyone, the title says it all. I would need it for wildlife photos (of course ). At the moment I have a 70-300 IS USM (not L) which is very soft, not happy with it anymore and need to step up. Is it still worth to purchase the mark I version of this lens? The mark II looks like a majestic lens, but it is quite expensive and very hard to find on the used market (at least where I live). On the other hand, the mark I is very easy to find second hand. Also, even though I never tried it, to me the push-pull system seems a better option to quickly focus on a fast moving subject. But, the lack of proper sealing is a concern on the long term, especially if buying second hand.... I am also considering a 70-300 L IS USM which can be found for a similar price of the 100-400 L mark I (second hand of course). This only because the 70-300 is a newer model with a better IS. But is it worth losing those 100mm? Thoughts?