Ventajas
Exxon provides a very disciplined approach to managing corporate direction and thus is relatively stable. In general, the pension and 401k are hard to beat benefits. You have an opportunity to work on some of the largest projects in the world.
Desventajas
Exxon is NOT an innovator, and requires it's engineers be bureaucrats rather than solve problems. Work and culture are abysmal environments, based on fear and punishment. Security and controls drive every aspect of daily business, and money is wasted for this purpose. It's approach to diversity and inclusion is an embarrassment. ExxonMobil does not branch out in the way it approaches today's energy challenges -- the only card they are willing to play is oil. No investigation in solar, wind, biofuels, etc.