HC Start, the defensive side is the best one for me, offensive is if you are getting hit really HARD.
Why is it amazing?
Simply because it takes half if not even less time to build than the usual run to the mill nubby 10k sp/sw build, which is both time consuming and the swords move at the speed of oxen.
It's still effectively despite having such a small build time and effective, fully build defensive village provided HC strat is used could rebuke 1.3-1.5 nukes, albeit the sp/sw has more strength, the other pros greatly outweigh the possibility of using Heavy Cavalry instead of the swords, the HC allows you to snipe if you're a lazy bugger and missed the times while being preoccupied elsewhere.
The HC travel ALOT faster than the swords, allowing swift stacking provided the area is clustered, the HC also offer some of the offensive power which is greater in comparison with the swords, granted the drain on the Iron is great, but when you're at the later stage in game it pays off greatly, seeing as you have versatile units which are able to move between villages quickly. Some nub tried to attack me by noble, 4 hours away, when they came the village had over a 50k HC in it and not as many spears, I was bored and wanted to reduce the shock as well as make him sweat for his ODA
Who would use SP/SW?
The nubs and the turtles, same thing those are.
It's kinda ghey on tech worlds as some of the tribes insist that sw are level 3 as well, which is kinda lame so you have to compromise and restore tech levels on EVERY damn village you take.