SQL Server query performance using constants vs. variables

Question

I'm wondering why this query with constant values takes about 2 minutes:

SELECT LeistungID,
       NULL AS EKK,
       NULL AS EKH,
       SUM(KostenKunde) AS KostenKunde,
       SUM(KostenHaendler) AS KostenHaendler,
       SUM(Anzahl) AS Anzahl,
       MwSt
FROM vauftragkostenporto2
WHERE kundenid = 676523
  AND druckam BETWEEN '1.2.2022' AND '28.2.2022'
GROUP BY LeistungID,
         Mwst;

Whereas the same query with parametersruns 50 minutes:

DECLARE @Start AS smalldatetime;
DECLARE @End AS smalldatetime;
DECLARE @KundenID AS int;

SET @KundenID = 676523;
SET @Start = CAST(CAST(2022 * 10000 + 2 * 100 + 1 AS varchar(255)) AS smalldatetime);
SET @End = DATEADD(MM, DATEDIFF(MM, -1, @Start), -1);

SELECT LeistungID,
       NULL AS EKK,
       NULL AS EKH,
       SUM(KostenKunde) AS KostenKunde,
       SUM(KostenHaendler) AS KostenHaendler,
       SUM(Anzahl) AS Anzahl,
       MwSt
FROM vAuftragKostenPorto2
WHERE KundenID = @KundenID
  AND DruckAm BETWEEN @Start AND @End
GROUP BY LeistungID,
         Mwst;