Wasn't THAT long ago, although 3 seasons is a long time.
In general, Tuchel would probably be far better in knockouts, whilst Xavi is better in league play and getting 3 points every week.
Another issue with Tuchel is he tends to fall out with his boards quickly and considering the politics at play in this club/poor finances he may very quickly become unhappy and the wheels would start to come off the bus.
Don't think he falls out that quickly
At Chelsea he never fell with Marina. Bohley didn't want him and ousted him in first bad spell