The Profession system, introduced in Season 1 and carried forward every season since, is a specialization choice with its own dedicated skill tree. Engineer focuses on economy and building speed - faster construction, better resource output, and general account growth. War Leader (sometimes called Warlord) focuses on combat - march capacity, rally strength, and direct battle bonuses.
There's no universally "correct" choice - it depends on your role in your alliance and your own playstyle. Members who focus on economy, city development, and supporting others tend to lean Engineer. Members expected to lead rallies, hold key positions, or carry combat events tend to lean War Leader. Talk to your alliance leadership if you're unsure which role they need filled.
Skill Points earned through the profession tree should be spent deliberately rather than reactively - review the available skill breakpoints before committing points, since some skills are far more impactful than others at the same point cost.