Statistically there's a 75% chance of progressing if you play the second leg at home...
Pity Juventus suck when it comes to this "statistic".
Arsenal, Liverpool, Chelsea, Bayern Munich, Benfica...all played away from home first. We lost all of these ties, most of them convinclingy.
The only "significant" wins I remember when playing at away first were against Celtic, Fiorentina and Lyon. All significantly worse than teams like Madrid.