You could buy the 8 and always be wondering if you should have bought the 10.
If you get the 10 you will know you have the most aperture you can fit into an average car.(without going to much pricier options).
I guess it comes down to what you want to spend on this new hobby. For a newcommer who isnt sure that they want to splash great amounts of cash the 8 gets almost universal recommendation as it is such great value. If cost isnt a problem go the 10.
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