I recently posted about a price drop for the 70-300 IS USM lens on Amazon. As of this post it is selling for $400 or just under.  This is the best price I have ever seen this lens sell for.   That prompted a few questions, comments and emails with thoughts and questions about the 70-200 f/4 L that is just a bit more.  The 70-200 f/4 L is selling new for just under $600 and you can buy a used copy for just under $500.   70-200 f/4 L lens is a nice lens.  It is an excellent value, very sharp and renders colors so nicely.  The 70-300 is very nice too, but it isn't L glass, it does however provide you with an extra 100mm and Image Stabilization (IS).   So which would I buy?[Photo samples coming soon]If I was a wildlife shooter on a budget or someone that wanted a zoom to carry around all day/on hikes/walkabouts I would pick the 70-300 IS USM. It is the lightest of the bunch at 1.39 lbs and having that extra 100mm is really nice where wildlife is concerned. It still won't feel like enough if you are trying to get those amazing national geographic like shots but it does a good job and the IS can be very helpful, it is even possible to shoot some video and use the IS for smoother action.  One bummer, the lens is USM but not full time manual focus, this is a lens you really want to use with back button focusing. Buy the 70-300 IS USM from Amazon, your purchase helps support this site.If I was a portrait or wedding photographer on a budget the 70-200 f/4 L USM is an excellent lens to take people photos, any photos really but at 1.55lbs it is starting to get heavy and won't be much fun to carry around all day. Buy the 70-200 f/4 L USM from Amazon.There is also the 70-200 f/4 L IS USM, the difference between the lens above is IS, 1/4 pound heavier and about $600 more for a total of just under $1200.  I believe it is slightly better optically but I have never actually shot with this lens so I can't say for sure.   Again, IS is useful in these longer lenses and this could be used by a sports photographer or a wedding photographer on a budget, though some might scoff at the idea that this is a budget minded lens.  Buy the 70-200 f/4 L IS USM from Amazon.And one more lens, because Luke asked ;), the 70-200 f/2.8L USM , we are now getting into dreamy territory.  Not a huge amount of image quality difference from the 70-200 f/4 but you get the constant f/2.8, excellent for indoor sports photographers and wedding photographers.  But this lens is HEAVY, weighing in at 2.89 lbs with a giant filter size of 77mm.  It also cost over $1200. Buy the 70-200 f/2.8 L USM from Amazon.And for another $1000 on top of that you could pick up the 70-200 f/2.8 L IS USM II lens or the original for slightly cheaper.  Both are excellent lenses, though very heavy and very expensive. There are also third party lenses like the Sigma and Tamron 70-200 but I have not been happy with the quality of any of the copies I tried. 70-300 IS USM - $40070-200 f/4 L USM - $60070-200 f/4 L IS USM - $120070-200 f/2.8 L USM - $120070-200 f/2.8 L IS II USM - $2100