List.ToArray() vs Get underlying list array

ToArrayVsTakeArrayBenchmark.cs

using System;
using System.Collections.Generic;
using System.Runtime.InteropServices;
using BenchmarkDotNet.Attributes;

namespace Benchmarks
{
    [MemoryDiagnoser]
    [ShortRunJob]
    public class ToArrayVsTakeArrayBenchmark
    {
        [Params(64, 128, 256, 512)]
        public int Max { get; set; }

        [Benchmark(Baseline = true)]
        public Span<int> ToArray()
        {
            var list = new List<int>();
            for (var i = 0; i < Max; i++)
            {
                list.Add(i);
            }

            return list.ToArray();
        }

        [Benchmark]
        public Span<int> TakeArray()
        {
            var list = new List<int>();
            for (var i = 0; i < Max; i++)
            {
                list.Add(i);
            }

            return CollectionsMarshal.AsSpan(list);
        }

        [Benchmark]
        public Span<int> ToArrayWithInitialCapacity()
        {
            // Half to force reallocation
            var list = new List<int>(Max / 2);
            for (var i = 0; i < Max; i++)
            {
                list.Add(i);
            }

            return list.ToArray();
        }

        [Benchmark]
        public Span<int> TakeArrayWithInitialCapacity()
        {
            // Half to force reallocation
            var list = new List<int>(Max / 2);
            for (var i = 0; i < Max; i++)
            {
                list.Add(i);
            }

            return CollectionsMarshal.AsSpan(list);
        }

    }
}

Results:

Method	Max	Mean	Error	StdDev	Ratio	RatioSD	Gen 0	Gen 1	Gen 2	Allocated
ToArray	64	365.3 ns	679.83 ns	37.26 ns	1.00	0.00	0.2217	-	-	928 B
TakeArray	64	373.6 ns	488.58 ns	26.78 ns	1.03	0.16	0.1545	-	-	648 B
ToArrayWithInitialCapacity	64	290.3 ns	347.33 ns	19.04 ns	0.80	0.06	0.1779	-	-	744 B
TakeArrayWithInitialCapacity	64	247.9 ns	270.54 ns	14.83 ns	0.68	0.03	0.1106	-	-	464 B
ToArray	128	741.2 ns	288.36 ns	15.81 ns	1.00	0.00	0.4110	-	-	1720 B
TakeArray	128	629.0 ns	576.28 ns	31.59 ns	0.85	0.04	0.2823	-	-	1184 B
ToArrayWithInitialCapacity	128	502.2 ns	427.99 ns	23.46 ns	0.68	0.04	0.3300	-	-	1384 B
TakeArrayWithInitialCapacity	128	420.8 ns	27.06 ns	1.48 ns	0.57	0.01	0.2027	-	-	848 B
ToArray	256	1,453.5 ns	1,499.73 ns	82.21 ns	1.00	0.00	0.7839	-	-	3280 B
TakeArray	256	1,117.7 ns	1,342.71 ns	73.60 ns	0.77	0.07	0.5322	-	-	2232 B
ToArrayWithInitialCapacity	256	948.8 ns	576.27 ns	31.59 ns	0.65	0.03	0.6351	-	-	2664 B
TakeArrayWithInitialCapacity	256	775.4 ns	701.59 ns	38.46 ns	0.54	0.06	0.3862	-	-	1616 B
ToArray	512	2,360.1 ns	1,180.88 ns	64.73 ns	1.00	0.00	1.5221	-	-	6376 B
TakeArray	512	2,162.8 ns	705.05 ns	38.65 ns	0.92	0.02	1.0262	-	-	4304 B
ToArrayWithInitialCapacity	512	1,897.1 ns	738.74 ns	40.49 ns	0.80	0.02	1.2474	-	-	5224 B
TakeArrayWithInitialCapacity	512	1,598.0 ns	2,882.06 ns	157.98 ns	0.68	0.07	0.7534	-	-	3152 B