I like +1/-2 because it leads to counterplay and an interesting balance between saves and attack rolls. Save spells can't get that easy +1 to hit but they don't have to worry about getting hit by -2 penalties. +2/-0 is clean but it's still a straight buff to ranged weapons while offering nothing to save based spells.
Originally Posted by DragonSnooz
Part of me would prefer high ground acting as a variant of cover. It'd be more interesting if (Assuming high ground Advantage/Disadvantage is removed):
A character could get cover for moving characters behind another allied character [Ally(+2AC)---Ally---Enemy]
A character could get cover for standing on an elevation at least 12 feet higher on the vertical axis [Ally---15 foot hill---Enemy(+2AC)]
Then we can have more clarity on to-hit throughout the whole game. (It could also work as a -2 to-hit).
In 5e, cover grants an equal bonus to Dex STs, which could help address your point @Rack. High ground bonus of +2 to attack could also increase the save DC of any DEX ST spells you use.