Interesting, I've pretty much entirely replaced brunch with webpack in my projects over the last few years, and found it much easier. The larger adoption and active community made it a lot easier to move forward when encountering webpack issues; surely that's thanks to the rapid spread of react, but if it means I spend less time wading through build problems in my non-react projects then that's fine with me.
What Sort of problems did you come across with Brunch that Webpack solved for you?