Falla to prevail
Falla managed to cause one of few upsets in round one, by beating huge John Isner. Not many people gave him a chance in this matchup, but Colombian managed to control Isner's serve, saving one match point on the way, and three break points in deciding set.
While Falla is not, nor even be, a great player, he can be very solid on the baseline, and damage his opponents with strong forehands. Personally I think that if he will manage to control Mahut serve as well, he should be able to gain advantage in the rallies.
Mahut is one of few players left these days who is regulary using serve&volley playing style, something very rare now, but it can be a deadly weapon, as Mahut proved in his win over Andy Murray two weeks ago.
However, such playing style can be a double edged sword, and Mahut had huge problems with Paolo Lorenzi in first round, and Paolo Lorenzi is not exactly second Roger Federer.
Falla should be dominant in his own service games, and Mahut can be unstable at times. Alejandro on the other hand two years ago had played fantastic game against Roger Federer on Wimbledon, coming very close to beating the King, thus he can deliver also on grass. With all due respect to Mahut and his achievements on grass, Falla represents decent value here.