I see their run on X Factor very different from each other, there might be a comparison just because they are the best singers in their respective season, as well as being from another country, but besides that everything is completely different.
Andrea was a power vocalist whose main strenght was that, singing big diva ballads and just captivating the whole audience just by using his voice. He was never in the bottom 2 and during the whole competition he was almost favorite to win.
Saara on the other hand has a huge voice, but what makes her more appealing is her ability to perform, as most of her performances have involved dancing and moving around, instead of just standing singing a ballad. Also, she came into the competition as what seemed to be just "fodder" for the producers, where her being in the bottom 2 the first two weeks projected that she wouldn't last past week 5, but against odds now she is in the top 4, and has become my personal favorite in the competition (even after I used to dislike her a lot since the 4 chair challenge, she has completely changed that around for me).
I don't think she is this year's Andrea Faustini at all.