struct array vs object array c#

public struct HelloStruct
    {
        public int[] hello1;
        public int[] hello2;
        public int hello3;
        public int hello4;
        public byte[] hello5;
        public byte[] hello6;
        public string hello7;
        public string hello8;
        public string hello9;
        public SomeOtherStruct[] hello10;

    }

    public struct SomeOtherStruct
    {
        public int yoyo;
        public int yiggityyo;
    }

    public class HelloClass
    {
        public int[] hello1;
        public int[] hello2;
        public int hello3;
        public int hello4;
        public byte[] hello5;
        public byte[] hello6;
        public string hello7;
        public string hello8;
        public string hello9;
        public SomeOtherClass[] hello10;

    }
        public class SomeOtherClass
    {
        public int yoyo;
        public int yiggityyo;
    }

 static void compareTimesClassVsStruct()
    {
        HelloStruct[] a = new HelloStruct[50];
        for (int i = 0; i < a.Length; i++)
        {
            a[i] = default(HelloStruct);
        }

        HelloClass[] b = new HelloClass[50];
        for (int i = 0; i < b.Length; i++)
        {
            b[i] = new HelloClass();
        }
        Console.WriteLine("Starting now");
        var s1 = Stopwatch.StartNew();
        for (int i = 0; i < _max; i++)
        {
            a[i % 50].hello1 = new int[] { 1,2,3,4,i % 50 };
            a[i % 50].hello3 = i;
            a[i % 50].hello7 = (i % 100).ToString();
        }
        s1.Stop();

        var s2 = Stopwatch.StartNew();
        for (int j = 0; j < _max; j++)
        {
            b[j % 50].hello1 = new int[] { 1,j % 50 };
            b[j % 50].hello3 = j;
            b[j % 50].hello7 = (j % 100).ToString();
        }
        s2.Stop();

        Console.WriteLine(((double)(s1.Elapsed.TotalSeconds)));
        Console.WriteLine(((double)(s2.Elapsed.TotalSeconds)));
        Console.Read();

    }

这里发生了一些我想要了解的事情.

首先,由于数组存储结构,当我尝试使用索引操作从数组访问结构时,我应该获得结构的副本还是对原始结构的引用？在这种情况下,当我在运行代码后检查数组时,我得到了变异的struct值.为什么会这样？

其次,当我比较CompareTimesClassVsStruct()中的时间时,我得到大致相同的时间.这背后的原因是什么？是否有任何情况下使用结构数组或对象数组会胜过另一个？

谢谢