The problem is that even with a better spec machine the loading screen will still be there with somewhat shorter loading time.
Given what I see right after exiting map view, where objects seems to required a complete reload (visually supported by objects reappearing and the sky truning from green back to blue), my guess is that the 3D rendering is completely disabled when in map, which is what causing the game to enter loading screen, and why the loading time is varying between different machine.

Correction: 3d model seems to be still rendered after more testing, texture however seems to reload everytime.

@SmallBlackSheep
OFP did not suffer the same problem, the map seems to be an direct overlay above normal 3d rendering as evident by a single pixel line at the edge of the screen where the texture match the 3d rendering outside map view.

Edit: One thing I want to see is if disabling map ground texture would help speeding up loading and unloading of map view.