>>1994362In theory the 777X is not a bad plane, it could be great in fact. The original version of the plane was fantastic at its introduction. A few significant upgrades is honestly all that's needed for it to stay competitive, but the flying public doesn't really have faith in Boeing to deliver a quality aircraft. Deservedly so, this due almost entirely to all the bad press Boeing has earned itself. The airlines as well don't have infinite patience either as its languishes in production/certification hell. It's difficult to replace a 777 with an A350 especially with the new variant's even more impressive capacity but it is an option.
Age isn't such clear cut simple factor to consider - the A320 is just as old as the 777 and its neo is the belle of the ball when it comes to orders.
While I just defended the 777, I like the A350. I like big twins and I cannot I lie. The A350 is one of the best planes flying today alongside the A220 but unlike the A220 it doesn't have as unique a character to it. At least it doesn't require as frequent engine maintenance however.