SQL 2012 :: Find All Rows WHERE DATETIME Within DATE

What would be the most economy solution for this WHERE, I see the code where we have covnert to 101 type on both sides of equation, which I tnink is not right.

So I'm thinking to put it on the left like this, just curiouse is this the best solution, I also heard that TSQL interpret between even better , here I'm really care abour performance.

declare @DATE DATE = '01/14/2014'
--A:
SELECT * FROM TT
WHERE CAST( TT.DATETIME AS DATE) = @DATE

--B:
SELECT * FROM TT
WHERE TT.DATETIME >= @DATE and TT.DATETIME < DATEADD(D,1,@DATE)