StringGCMagic.cs

void Update()
{
    int count = 1000;
    string format = "|{0} {1}|";

    Profiler.BeginSample("ToString");
    for (int i = 0; i < count; i++)
    {
        text1.text = i.ToString() + " " + i.ToString();
    }
    Profiler.EndSample();

    Profiler.BeginSample("Concat");
    for (int i = 0; i < count; i++)
    {
        text1.text = string.Concat(i, " ", i);
    }
    Profiler.EndSample();

    // The StringBuilder creation is in the loop on purpose for those

    Profiler.BeginSample("StringBuilderNew");
    for (int i = 0; i < count; i++)
    {
        StringBuilder sbl = new StringBuilder();
        sbl.AppendFormat(format, i, i);
        text1.text = sbl.ToString();
    }
    Profiler.EndSample();

    Profiler.BeginSample("ConcatFormatNew");
    for (int i = 0; i < count; i++)
    {
        StringBuilder sbl = new StringBuilder();
        sbl.ConcatFormat(format, i, i);
        text1.text = sbl.ToString();
    }
    Profiler.EndSample();

    StringBuilder sbr = new StringBuilder();

    Profiler.BeginSample("StringBuilderReuse");
    for (int i = 0; i < count; i++)
    {
        sbr.AppendFormat(format, i, i);
        text1.text = sbr.ToString();
        sbr.Length = 0;
    }
    Profiler.EndSample();

    sbr.Length = 0;

    Profiler.BeginSample("ConcatFormatReuse");
    for (int i = 0; i < count; i++)
    {
        sbr.ConcatFormat(format, i, i);
        text1.text = sbr.ToString();
        sbr.Length = 0;
    }
    Profiler.EndSample();

    Profiler.BeginSample("StringBuilderCache");
    for (int i = 0; i < count; i++)
    {
        StringBuilder sb = StringBuilderCache.Acquire();
        sb.AppendFormat(format, i, i);
        text2.text = sb.GetGCFreeStringAndRelease();
    }
    Profiler.EndSample();

    Profiler.BeginSample("StringBuilderCache-ConcatFormat");
    for (int i = 0; i < count; i++)
    {
        StringBuilder sb = StringBuilderCache.Acquire();
        sb.ConcatFormat(format, i, i);
        text3.text = sb.GetGCFreeStringAndRelease();
    }
    Profiler.EndSample();
}

Result : https://i.imgur.com/8aqgCP0.png