5e. It works most clearly with the central mechanics of the game.
Yeah, just making it a saving throw for the undead is nice. 5e's approach is the only one I could run from memory without referencing the rules. There's a lot of value in that!
I like the OED Expanded rule.
- Banish the Unhallowed: Present the relic & recite the liturgy of life & death
1d6 + (Cleric Level – 5) = highest Hit Die of Undead that must flee or cower while liturgy continues. 2d6 creatures are affected (lowest Hit Die first). If Cleric’s level 4 more than Undead Hit Dice, it is destroyed;
That's a nice attempt to convert the original table into a formula. It's pretty rough on the Cleric though! The best undead HD they can affect is their level + 1, and the spread is centered well below their level. 1d6 + level – 4 is actually a better match to the table at most levels. Also easier to remember since it's the same number as the gap needed between level and HD to destroy rather than turn.
My other concern is it doesn't account for the progression slowing down at level 9+ (in the expanded AD&D table). E.g. level 13 Clerics aren't supposed to automatically destroy 9 HD vampires.
That name level step change appears in a lot of places in the classic system math, making it tough to convert tables into formulae.
I like formulas more than having to consult tables, so not the OD&D/AD&D versions for me.
I also don't like Turn Undead to end up being just another damage, so not the 4e version either.
That leaves the 3e and 5e versions... I'm fine with both but maybe the 3e version feels a bit more unique due to the "turning damage" mechanics instead of the standard save for each target.
I'm with you, I'd prefer to not use tables and for turning to feel unique.
0e-3e have a two roll model where the first roll determines whether the turning is effective at all, and the second roll determines the magnitude of the effect (how many creatures/HD are turned).
The two role model provides some tactical wrinkles that are lost in 5e. Because the turning effect can be "soaked up" by weaker types, it might be wise to knock them off first before attempting to turn.
3e Turning affects undead in order of proximity to the Cleric, which is even more interesting. Low level fodder will usually be in front of the higher level leader type in a mixed encounter, but the Cleric might be able to maneuver around and Turn the leader first by blasting them up close. That's cool.