Which MacBook Pro should I get?

I have a Lenovo Flex 2 right now and it's the worst laptop I've ever owned. It's nothing but problems so I decided that I wanted to transition over to Apple because I just really like their products more. I want to get the MacBook Pro 13 with retina display and 8gb of Ram but I'm stuck on the storage. Should I get 128gb or 256gb? I'm going to down load Microsoft office for Mac on the computer for school. I also have a lot of music and photos that would go on this computer. The 256gb is three hundred dollars more so I need to know is it worth it or should I go with the 128gb and just buy an external hard drive?

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