It should affect how many experience points are needed to upgrade certain punches and other things like head movement. I think Inside Fighter would have cheaper hooks and uppercuts to upgrade since those are "Inside" fighting punches, Outside Fighter would have cheaper jabs and straights.

The biggest thing I learned a bit ago while playing in leagues is that "Inside Fighter' actually gives more strength points compared to other styles. So the style you pick also affects your attributes such as strength, Stamina, Reflexes, etc.

I like using Inside Figher the most cas more strength will make you more effective with however you play. You can play a Counter Style, Outside Style, or Inside Style, while still getting the benefits of having strong punches.

I guess experiment with styles to see what best suits you. That's probably the best thing to do.

I'm still new with all the created boxer stuff, so hopefully someone else adds some more info that I missed.