I'm so over trying to make my 70-300mm work for wildlife it's literally impossible to get anything decent when the animals are more than fifty feet away. I'm heading up to some marshy areas in Oregon next month for the migration and I desperately need more reach for my D500 but the Sigma lineup is giving me a massive headache. I've got maybe $1400 saved up and I'm totally torn between two or three paths here.

My logic was originally to just grab the 150-600mm Contemporary because it's so much lighter and I do a lot of walking but then I started reading these horror stories about the autofocus being inconsistent in low light or when the birds are moving fast. So then I looked at the 150-600mm Sport version which everyone says is built like a tank and has better optics but it weighs like six pounds? I'm not a bodybuilder I just want to take pictures of eagles. Is the extra weight of the Sport version actually worth the trade-off for better sealing and slightly faster AF or is the Contemporary good enough if I'm mostly shooting in decent light?

Then there's the 60-600mm which some people swear by but it's stretching my budget and I'm worried it's a jack of all trades master of none situation. I keep going back and forth on whether I should prioritize the portability of the C or the durability of the S. I've seen some guys say the Contemporary is just as sharp if you stop it down but others say it's a blurry mess at 600mm. I'm just frustrated because every review says something different and I dont want to drop a grand and a half on something that's gonna frustrate me in the field. Does the Sport really autofocus that much faster on a Nikon body or is it mostly just the build quality youre paying for...