ToArray vs ToList vs ToImmutableArray vs ToImmutableList

Program.cs

using System;
using System.Collections.Generic;
using System.Collections.Immutable;
using System.Linq;
using BenchmarkDotNet.Attributes;
using BenchmarkDotNet.Running;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main()
        {
            BenchmarkRunner.Run<Bench>();
        }
    }

    public class Bench
    {
        private const int _count = 10000;

        IEnumerable<int> Do(Func<IEnumerable<int>, IEnumerable<int>>f) =>
            f(f(Enumerable.Range(0, _count)).Where(x => x % 2 == 0));


        [Benchmark]
        public IEnumerable<int> ToImmutableArray() => Do(x => x.ToImmutableArray());

        [Benchmark]
        public IEnumerable<int> ToArray() => Do(x => x.ToArray());

        [Benchmark]
        public IEnumerable<int> ToList() => Do(x => x.ToList());

        [Benchmark]
        public IEnumerable<int> ToImmutableList() => Do(x => x.ToImmutableList());
    }
}

Slightly modified:

public class Bench
{
    private const int _count = 10000;

    IEnumerable<int> Do(Func<IEnumerable<int>, IEnumerable<int>> f) =>
        f(f(Enumerable.Range(0, _count)));

    [Benchmark]
    public ImmutableArray<int> ToImmutableArray() => (ImmutableArray<int>)Do(x => x.ToImmutableArray());

    [Benchmark]
    public int[] ToArray() => (int[])Do(x => x.ToArray());

    [Benchmark]
    public List<int> ToList() => (List<int>)Do(x => x.ToList());

    [Benchmark]
    public IImmutableList<int> ToImmutableList() => (IImmutableList<int>)Do(x => x.ToImmutableList());
}

Result:

// * Summary *

BenchmarkDotNet v0.13.6, Windows 11 (10.0.22621.1992/22H2/2022Update/SunValley2)
Intel Core i7-7700K CPU 4.20GHz (Kaby Lake), 1 CPU, 8 logical and 4 physical cores
.NET SDK 7.0.306
  [Host]     : .NET 7.0.9 (7.0.923.32018), X64 RyuJIT AVX2
  DefaultJob : .NET 7.0.9 (7.0.923.32018), X64 RyuJIT AVX2

|           Method |       Mean |     Error |    StdDev |
|----------------- |-----------:|----------:|----------:|
| ToImmutableArray |   5.024 us | 0.0841 us | 0.1002 us |
|          ToArray |   6.907 us | 0.0611 us | 0.0510 us |
|           ToList |  17.291 us | 0.2834 us | 0.2512 us |
|  ToImmutableList | 178.526 us | 0.9276 us | 0.7242 us |