意外にパワフル！？NSUserDefaultsの書き込み、読み込み速度について ref: http://qiita.com/yuky_az/items/13dfc156db118db04f17

UserDefaultsSample.m

- (void)viewDidLoad
{
    [super viewDidLoad];

    mArray = [NSMutableArray new];

    NSArray *array = @[@"赤",
                       @"青",
                       @"緑",
                       @"黄",
                       @"白"];

    int repeatNumber = 10000;
    for (int i = 0; i<repeatNumber; i++) {
        NSMutableString *string = [NSMutableString new];
        for (int j = 0; j<100; j++) {
            int randNum = arc4random()%[array count];
            [string appendString:array[randNum]];
        }
        [mArray addObject:string];
    }
}

-(IBAction)saveTapped:(id)sender{
    NSDate *beforeDate = [NSDate date];
    NSUserDefaults *uD = [NSUserDefaults standardUserDefaults];
    [uD setObject:mArray forKey:@"Array"];
    [uD synchronize];
    NSTimeInterval interval =fabs([beforeDate timeIntervalSinceNow]);
    NSLog(@"Saving took %f seconds!", interval);
}

-(IBAction)loadTapped:(id)sender{
    NSDate *beforeDate = [NSDate date];
    NSUserDefaults *uD = [NSUserDefaults standardUserDefaults];
    NSMutableArray *loadedArray = [uD objectForKey:@"Array"];
    NSTimeInterval interval =fabs([beforeDate timeIntervalSinceNow]);
    if (loadedArray) {
        NSLog(@"Loading took %f seconds!", interval);
    }
}

-(IBAction)changeTapped:(id)sender{
    NSDate *beforeDate = [NSDate date];
    mArray[0] = @"ABC";
    NSTimeInterval interval =fabs([beforeDate timeIntervalSinceNow]);
    NSLog(@"Changing took %f seconds!", interval);
}