I suposse it depends on your hosting? If you host in Webflow servers should be faster...
Both load fast, both run on CDNs (content delivery networks). How Google Fonts or Custom Fonts perform for you, for your site, will depend mainly on how many custom fonts you are trying to load and the font sizes. The more fonts you load, the longer it will take for your site to load.
Definitely in most cases, loading font from Google Fonts or Custom Webflow Font is faster than loading a font from a single non-cdn hosted server (in most cases).
Here is some more information relating to Google Fonts and Performance: