switching_view_based_on_size.py

def find_largest_3dview_and_switch():
    collected_areas = []
    for window in bpy.context.window_manager.windows:
        for area in window.screen.areas:
            if area.type == 'VIEW_3D':
                size = area.height * area.width
                collected_areas.append([size, area, window])
    
    # no 3dview found? use texeditor.
    if len(collected_areas) == 0:
        bpy.ops.render.render('INVOKE_DEFAULT')
        return
        
    # else use largest 3dview.
    for area in sorted(collected_areas, reverse=True):
        area[1].type = 'IMAGE_EDITOR'
        w = area[2]
        override = {'window': w, 'screen': w.screen, 'area': area[1]}
        bpy.ops.render.render(override)
        return