Procedure I wrote which does this all for you:

create procedure dbo.fn_tablecompare(@table1 varchar(20), @table2 varchar(20))

as

begin

declare @sql nvarchar(max)

set @sql = ''

select @sql = @sql + 'select max(len(' + COLUMN_NAME + ')) columnlength, ''' + column_name + ''' columnname from ' + TABLE_NAME + ' union ' from INFORMATION_SCHEMA.COLUMNS where TABLE_NAME = @table1

set @sql = LEFT(@sql,LEN(@sql)-5)

set @sql = 'select isnull(columnlength,0) columnlength, b.character_maximum_length, columnname from (' + @sql + ') a join information_schema.columns b on (a.columnname = b.column_name) where b.table_name = ''' + @table2 + ''' and a.columnlength > b.character_maximum_length'

exec (@sql)

end