Jeff makes an excellent post here on the different edition of D&D and their differences.
Which is to say the difference are largely inconsequential for older editions and debating their difference resulting in flying monkey poo.
And I agree wholeheartedly. Not because Jeff is a cool guy and I like his writing. But of my experience in writing Points of Light.
Before I started Points of Light with Dwayne I had to do some preparation. Basically I went through the OGL D20 SRD and found every monster mentioned from OD&D to 2nd Edition. I also researched the various magic items.
What I found that these elements carried over from edition and to edition most unchanged. Because I had no room for anything but minimal stats that meant the Points of Light will work for just about any edition of D&D.
Because of the influence of D&D on our hobby, the bits and pieces of D&D are found nearly every fantasy RPG. So Points of Light's usefulness goes beyond D&D itself.
Now if you are writing a rule supplement then likely you will need to pick a specific version to work off of. It just the nature of the beast. But even then Class, Level, Hit Dice, Armor Class are not really hard to convert between the older editions. Special Powers often just translate over as well.
So Jeff is very much right that debating older editions boils down to slinging monkey poo at each other.
So put the monkey poos down!