What is the difference between these two LINQtoSQL statements?

Question

These two statements look equally logical to me, but they lead to the generation of different SQL:

#1 
var people = _DB.People.Where(p => p.Status == MyPersonEnum.STUDENT.ToString());
var ids = people.Select(p => p.Id);
var cars = _DB.Cars.Where(c => ids.Contains(c.PersonId));

#2 
string s = MyPersonEnum.STUDENT.ToString();
var people = _DB.People.Where(p => p.Status == s);
var ids = people.Select(p => p.Id);
var cars = _DB.Cars.Where(c => ids.Contains(c.PersonId));

Example # 1 does not work, but example # 2.

The generated SQL for the query var peopleis identical for both, but the SQL in the final query is different as follows:

#1
SELECT [t0].[PersonId], [t0].[etc].....
FROM [Cars] AS [t0]
WHERE EXISTS(
    SELECT NULL AS [EMPTY]
    FROM [People] AS [t1]
    WHERE ([t1].[Id] = [t0].[PersonId]) AND ([t1].[Status] = (CONVERT(NVarChar,@p0)))
    )

#2
SELECT [t0].[PersonId], [t0].[etc].....
FROM [Cars] AS [t0]
WHERE EXISTS(
    SELECT NULL AS [EMPTY]
    FROM [People] AS [t1]
    WHERE ([t1].[Id] = [t0].[PersonId]) AND ([t1].[Status] = @p0)
    )

Why is there such a difference?

Edit:

So far, all I have done to generate SQL is to check the query in the debugger. However, after setting up the logger, as John suggested, it seems that the real sql is executed differently.

#1 
SELECT [t1].[Id], [t1].etc ... [t0].Id, [t1].etc ...
FROM [Cars] AS [t0], [People] AS [t1]
WHERE ([t1].[Id] = [t0].[PersonId]) AND (EXISTS(
    SELECT NULL AS [EMPTY]
    FROM [People] AS [t2]
    WHERE ([t2].[Id] = [t0].[PersonId]) AND ([t2].[Status] = (CONVERT(NVarChar,@p0)))
    )) AND ([t1].[Status] = @p1)
-- @p0: Input Int (Size = 0; Prec = 0; Scale = 0) [2]
-- @p1: Input NVarChar (Size = 7; Prec = 0; Scale = 0) [STUDENT]

#2
SELECT [t1].[Id], [t1].etc ... [t0].Id, [t1].etc ...
FROM [Cars] AS [t0], [People] AS [t1]
WHERE ([t1].[Id] = [t0].[PersonId]) AND (EXISTS(
    SELECT NULL AS [EMPTY]
    FROM [People] AS [t2]
    WHERE ([t2].[Id] = [t0].[PersonId]) AND ([t2].[Status] = @p0)
    )) AND ([t1].[Status] = @p1)
-- @p0: Input NVarChar (Size = 7; Prec = 0; Scale = 0) [STUDENT]
-- @p1: Input NVarChar (Size = 7; Prec = 0; Scale = 0) [STUDENT]

Answer 1

First think of the dual nature of e Enum:

enum MyPersonEnum
{
  STUDENT, // implicit 1
  TEACHER, // implicit 2
  DIRECTOR = 10 // explicit 10
}

...

Assert.AreEqual(1, (int)MyPersonEnum.STUDENT);
Assert.AreEqual("STUDENT", MyPersonEnum.STUDENT.ToString());

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Answer 2

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