Currently I would put Barcelona ahead of Real Madrid. Because all the players of the Barcelona team play the match with great responsibility. On the other hand, if Real Madrid has a dedicated striker, I think the team will be complete.
You are free to put any team of your own mind in which area at the moment, but you also have to accept the fact that Barcelona have not been strong enough in the Champions League for the last two seasons. So Xavi will continue to try to make Barcelona strong again in the Champions League this season even though it won't be easy enough for him this season because Real Madrid won't necessarily be weak this season even if you say Real Madrid doesn't have a dedicated striker.