Hi,
Stats are stored in a binary large object called a statsblob. These are very small, even with very large tables, and you will not find any performance gains by cleaning them up.
You can see the blob by using a DAC to run the following code.
SELECT
OBJECT_NAME(s.object_id),
s.name,
DATALENGTH(o.imageval) / 1024. AS StatsSize_Kb
FROM
sys.stats AS s
INNER JOIN
sys.sysobjvalues AS o
ON s.object_id = o.objid
AND s.stats_id = o.subobjid
WHERE
OBJECTPROPERTY(s.object_id, 'IsSystemTable') = 0
ORDER BY
3 DESC;
