Most likely it is a preload issue. With the apt version, the libraries are already preloaded on your system, because they are shared and in use.

With the snap version, the application needs to load up the common core image, then load the set of libraries that are specific to the application. The core image can probably get preloaded, but the set of libraries that are specific to the application probably not. Definitely in the disk cache, but maybe not preloaded.