Personally, from what I have experienced, Netlify builds (preparing build like downloading dependencies, cloning the repo, etc. parts excluded) are way faster as compared to my local machine. The only problem is when you update your
package.json and it has to redownload your dependencies. So, that download might take some time depending on your dependencies size. But, even that process is faster for me than on my local machine.
The most important factor is the framework though. For example, I have used Gatsby and Hugo in the past months. Gatsby takes quite some time to build and it increases exponentially with the number of pages and images, but, Hugo, on the other hand is pretty fast. It takes like a few seconds to finish the build. I haven’t used NuxtJS much (except for a 2 paged website once), thus, commenting about its speed is not possible. However, I think I can say in general that it’d be faster than building on your local machine. That is true only if NuxtJS doesn’t build websites as fast as Hugo does, because while the actual build takes seconds, the preparation for build like setting up environment, downloading dependencies, etc., do take some time. So, that time does add up.
Here are the statistics in my case:
For a Hugo build, the actual build took 573 ms (25+ pages), while the rest of Netlify process took the total build time to 1 min 40 sec. This builds in around 12 sec on my local machine.
For a Gatsby build, the actual build took about 49 seconds (400+ pages) while the rest of Netlify process took the total build time to 1 min 54 sec. This builds in around 2 min on my local machine.
So, as you can see, in case of Hugo, Netlify builds are slower for me than my local builds if the complete time of deployment is considered. However, in case of Gatsby, the entire Netlify deployment process is done before the website builds on my local machine.
I hope this helps.