I would probably get the 300+1.4x, for these reasons:



  • IQ is still very good
  • Basically gives 2 lenses, a 300mm f/4 IS and a 420mm f/5.6 IS

<div>And the main reason:</div>
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  • The 300mm+1.4x has IS, which could be very helpful on such a long and slow lens.

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