Ok, so the new version is upgraded to Unity 5 and added in a whole lot of voice clips.
Is there any reason for me to install/play the original instead of the Director's Cut?

GOG did give us both versions.
Is it a matter of compatibility, that they provided both versions? What is the sys req for original WL2 compared to Director's Cut.

The Director's Cut also plays differently. It has new perks and abilities. AND, the laser weapons have different damage and do the maths different too. I played on the max difficult on the director cut and was A BIG MISTAKE. A single hit, not even critical, and your PC melts in agony. And at the end of the game, you will need like 3 misses from the enemy for reaching a cover. So, play on normal or the one before the last setting.

Also it is not a bad idea to play both versions :)

thanks. i found this at another forum.
gaming.stackexchange.com/questions/245087/what-is-new-in-the-directors-cut-of-wasteland-2

so i guess the original has less customisation? not sure what they mean by rebalancing all the weapons and items... i guess they made it tougher?

Just to be clear, you're saying the change in how it calculates hits causes your PC to overheat (in the Director's Cut version)?

That would make me only choose to play the original version.

i think he meant Player Character...

Erh, PC == Player Character. Though, I must admit that selection of words didn't help :P
I had Basically they are better, with exception of the laser weapons on the last difficulty setting.
But seriously, the changes are enough to play both versions by separated.

I think this is my 'Doh!' moment. So erm....Doh! ;)

The directors cut does a few things.

1) simplifies skill checks. This is the major good change, no more having to manually choose the person to do the action, the game just picks the right person.

2) Adds in perks and quirks, which makes your characters stronger than normal then the regular wasteland 2. The added in perks and quirks also help make non-rifles useful if you want to play that way. In the normal version assault rifles and snipers are king, and the rest useless. In the directors cut, they are still king, but other weapons can now actually be useful with the right perks, especially melee/unarmed. SMGS really are good with psychopath quirk, shotguns are ok, especially in late game if you can find powerful ones. Energy weapons are ok, heavy weapons still suck.