Comparison between Implicit conversion and Explicit conversion in SQL query

Implicit conversion

I have taken AdventureWorks2017 database for this below query demo.

In Implicit conversion, we are comparing a [AccounNumber] varchar() with a value, which is also a varchar and after running this query once with Actual execution plan and Statistics ON, we find the more CPU time used and execution plan shows warning. 

 SET STATISTICS TIME ON 

 SELECT per.FirstName, per.LastName, per.BusinessEntityID, cust.AccountNumber, cust.StoreID 
 FROM Sales.Customer cust
 INNER JOIN Person.Person per ON per.BusinessEntityID = cust.PersonID
 WHERE AccountNumber = N'AW00029594'
 GO

It shows more wired result when we run this query for 200 times, we found more CPU time and more execution time. approx more than 30 sec.

 SELECT per.FirstName, per.LastName, per.BusinessEntityID, cust.AccountNumber, cust.StoreID 
 FROM Sales.Customer cust
 INNER JOIN Person.Person per ON per.BusinessEntityID = cust.PersonID
 WHERE AccountNumber = N'AW00029594'
 GO 200

Explicit conversion 

Whereas in explicit conversion, It shows more nice result when we run this query for 200 times,  we found "0" CPU time and more execution time. approx less than 10 sec.

SET STATISTICS TIME ON 

 SELECT per.FirstName, per.LastName, per.BusinessEntityID, cust.AccountNumber, cust.StoreID 
 FROM Sales.Customer cust
 INNER JOIN Person.Person per ON per.BusinessEntityID = cust.PersonID
 WHERE AccountNumber = CONVERT(VARCHAR, N'AW00029594')
 GO 200

Conclusion: Try to avoid write query, which does implicit conversion. So, either compare value with same data type or convert it explicitly