I use an APS-C body for nature photography, so what I'm after the most is the reach and sharpness. Currently I have a Canon 55-250 IS STM. Do you think it would be reasonable to buy a 70-300 IS II USM? Do you think that this extra 50 mm is worth the cost (this lens is rather expensive but there is a significant cashback program on it now where I live). Also, it's an EF so it would be usable should I decide to buy a full frame body in the future. Any advice would be appreciated.