I know that. Endurance = more Health. Armour = Damage reduction = less health loss = more Health. They equate to the same thing indirectly. Same with Strength. Strength indirectly equates to the damage potential. The weapon may not hit as hard like for like but your additional strength makes up for that. But without knowing what each equates to I'm unable to make a decision on whether one piece of equipment is better than the other.
If you know all that, then you've answered your own question with your own knowledge already. If you didn't know anything already said, then you don't know all that.
Str will increase your damage by an i forget the exact amount per point if, and only if, you are a Sith Warrior/Jedi Knight (and their advance classes naturally). You can find out your damage breakdown by opening your character sheet, looking at the bottom left box with the Melee stats, hovering over Damage and Bonus Damage.
Endurance gives you 10 hp per 1 point of endurance over the base. That's it's effect right there. There is no correlation between endurance and armor so your question of Endurance vs Armor rating is rather confusing and not answerable.
You seem to be curious about these stats in an attempt to help you gear better. All I can really say on this note is, better gear will give you more strength and endurance and damage and a secondary stat or two (crit/surge/power/alacrity). So trying to compare incomparable stats is sort of moot. If numbers are green, equip it. You can read through these forums on suggested sweet spots for all stats to help you gear up properly too.
If you come to a choice of say, gaining X str but losing Y end, you have to ask yourself "Do i need more strength or health at this point?" and equip accordingly. You'll also notice as your leveling and gearing that most equipment types and mods designed for a class tend to have two paths... Path A. which will favor primary stat over endurance slightly (good options for the dps and heal roles)... and Path B. which will favor endurance over primary stat slightly (presumably good for tank roles). This is something to also keep in mind when deciding what to sacrifice for what when gearing up.
If that didn't answer your curiosity at all then I don't know if anyone will really understand what it is exactly you want to know.