Certainly if you made a trip-fighter or the like, you would stick with (sigh) the spiked chain. Otherwise, probably greatsword. However, I remember on the WotC boards when 3.0 switched to 3.5, a lot of hullabaloo over how Damage Reduction meant now instead of always wanting the +3 sword instead of the +1 flaming one (since the former could effect creatures that the later could not), you would want a +1 cold iron bludgeoning weapon, a +1 silver bludgeoning weapon, a +1 adamantine bludgeoning weapon, a +1 cold iron piercing weapon... (and so on).Funny you should say that - my table found that D&D3.x strongly encouraged get one weapon and sticking with it. You got the weapon that allowed/was best for whatever feat chain you intended to abuse and you stuck with it. Having to buy Weapon Focus (and Specialisation, etc., if a Fighter) on a per-weapon basis further locked you in. The only characters that ever swapped weapons around were the caster types, who would simply use (more often just carry for ages and never use) whatever weapon they had proficiency in that was most magical or looked coolest.
I also never heard of people taking weapon focus or specialization unless it was a PRC requirement (at least until we stopped worrying about the rules and just played for flavor).
I think the issue is that it is the martial-upgrade to the spear (let's ignore that a spear is totally a soldier's weapon and that a trident is a fishing implement used in gladiatorial fights specifically because it caused bloody-but-less-lethal wounds) that has not mechanical benefits for being martial (excepting I suppose that those without martial proficiency have a harder time throwing it back at you). 5e actually has quite a few sub-optimal choices-- great club, maul (a greatsword, but heavier and cheaper), mace (quarterstaff is equal, but can also be two-handed for more damage), etc.I saw a serious suggestion that the trident in 5e D&D is broken and needs to be fixed. Why? Because it costs more than a spear, weighs more than a spear, requires a narrower weapon proficiency than a spear, does the same damage as a spear, and doesn't give any fancy mechanical perks over a spear. So in a nut shell it's a heavier, clumsier, more expensive spear and that makes it broken. Sigh. Sub-optimal stuff seems to be a realism people don't want to deal with. Not everything is better, or even equally good.