SQL Server Pattern – Field = Parameter OR Parameter IS NULL

I am aware of the parameter sniffing issues associated with stored procedures written with a predicate like the following:

CREATE PROCEDURE [dbo].[Get] @Parameter INT = NULL AS BEGIN;
    SELECT [Field] FROM [dbo].[Table]
    WHERE [Field] = @Parameter 
    OR @Parameter IS NULL;
END;

Depending on the value of the parameter, Scalar or NULL on first execution, a plan is cached that will likely be sub optimal for the opposite value.

Assuming [Field] is scalar, and the clustering index on a table. What are the pros and cons to the following approaches to writing a stored procedure(s) to support the query:

Conditioned selects in same stored procedure

CREATE PROCEDURE [dbo].[Get] @Parameter INT = NULL AS BEGIN;
    IF(@Parameter IS NOT NULL) BEGIN;
        SELECT [Field]
        FROM [dbo].[Table]
        WHERE [Field] = @Parameter;
    END;
    ELSE BEGIN;
        SELECT [Field]
        FROM [dbo].[Table];
    END;
END;

Dynamic SQL within stored procedure

CREATE PROCEDURE [dbo].[Get] @Parameter INT = NULL AS BEGIN;
    DECLARE @sql NVARCHAR(MAX) = N'';
    SET @sql += N'SELECT [Field]'
    SET @sql += N'FROM [dbo].[Table]';

    IF(@Parameter IS NOT NULL) BEGIN;
        @sql += N'WHERE [Field] = @Parameter';
    END;

    SET @sql += N';';

    EXEC sp_executesql @sql N'@Parameter INT', @Parameter;
END;

Separate stored procedures

CREATE PROCEDURE [dbo].[Get] @Parameter INT = NULL AS BEGIN;
    SELECT [Field]
    FROM [dbo].[Table]
    WHERE [Field] = @Parameter;
END;

CREATE PROCEDURE [dbo].[GetAll] AS BEGIN;
    SELECT [Field]
    FROM [dbo].[Table];
END;