Well, we don’t really start a server on Android, we serve files through a web view interception mechanism. With Meteor 1.3, we did switch to a local server on iOS, and this actually makes file serving faster!
Although there is some overhead from loading the files, I suspect the problem with the splash screen has more to do with the way the launch-screen package works. Depending how you have this set up, it might wait for your data to be loaded before it goes away.
You may also want to give Meteor 1.3 a try, which could help improve mobile performance: