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Gaming is unspecific and macbooks are bad for gaming. Bootcamp is not an app.
Despite lack of info I am just gonna guess that the cpu upgrade would be a waste of $$$.
 
Gaming uses the GPU, not CPU, and coding/web design does not take a powerful CPU (unless you plan to compile large projects) so I think you'll be fine with the 2.6.
 
It's throwing money to the trash if you don't render 4K videos for several days straight.

Stick with the 2.5GHz variant.

Not to mention the cpu running hotting and potentially throttling more frequently than a normally slower but cooler variant.
 
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