Based on my benchmarking of .NET 5 & 6, it looks like many LINQ statements are twice as fast in 6. 

.NET Infographics 

Creating a Dapper Helper C# Class to Generate Parameterized SQL 

How Does the StringBuilder Work in .NET?  

up to 17.9% less memory required for .NET 5 FlexGrid row auto sizing.
rid painting is up to 1.3 times faster for .NET 5 than for .NET Framework 4.5.2.
fit the data in all columns up to 1.7 times faster for .NET 5.
 

Store Files in a File System, Not a Relational Database 

What Every Programmer Should Know About SSDs 

Overall, .NET 5 demonstrates a significant performance improvement over .NET Framework in XAP’s scenario. While there is still more work to do, the overall picture is clear that .NET 5 is phenomenally superior in most respects.