Since there were no more comments to this question and no solutions were provided. I've looked into this with both university and work colleagues and we came up with the following solution:
Use
SELECT TOP 1
T.ENTITY_NAME AS X
,T.SP_Y AS Y
FROM
dbo.TABLE AS T
WHERE
T.SP_Y = @p_Y
AND T.SP_EAT_ID in (15, 16)
ORDER BY
T.SP_EAT_ID desc
This was the chosen one due to be easier to read and achieving a similar performance to the first select.
For more details on the comparison. Please read the comment of "NeverJustHere" at 19-Feb-14.
Regards