Hi Marvin,
I broke down a bunch of stuff related to this in hashnode.com/ama/with-zurb-foundation-cj4ad29vl00…
The long and short of it is - Webpack is better (and faster) for JavaScript, but slower for SCSS (we've seen almost 2x slower on SCSS building). So if you're doing more of a static site that is mostly html & scss without tons and tons of JavaScript, it's probably still going to be better to use gulp for the scss. If you're heavy on the JS, there's advantages to moving completely to Webpack.
Most folks are using foundation-zurb-template for more static sites and prototyping, so we'll probably stick with gulp for that... at least until Webpack gets a faster scss compile. :)