To convert varchar to datetime : CONVERT(Datetime, '28/02/2014', 103)
return the datetime like February, 28 2014 00:00:00+0000
To convert datetime to varchar : CONVERT(VARCHAR(10), datetime_field, 103)
return something like '28/02/2014'
In both case you cannot compare it to this kind of text : '20140101'
You can change your text so both informations are ISO like : CONVERT(VARCHAR(10), CONVERT(Datetime, ent.Value, 103), 103) < '01/01/2014'
Or REPLACE(ent.Value,'/','') < '01012014'
But I don't think it's good to compare varchar => you can also do something like this : CONVERT(Datetime, '20140101', 112) :
CONVERT(Datetime, ent.Value, 103) < CONVERT(Datetime, '20140101', 112)
So your both field are in Datetime. ex : SQLFIDDLE DEMO