Title says it all: Do you prefer flanking or combat on your mounted units? I'm never quite sure. Flanking increases their survivability a lot. Units with combat are more likely to die, but at least they do some damage...
Flanking II also has the disadvantage, that Horse-units are immune to Firststrikes
I think flanking has it's place as a suicide unit in HA rushes. Where chances are very low like against a city spearman (or even just an archer in a hill city with 40%+ cultural defense) I find flanking better overall for the first attack than combat I.
I think the point of flankers in HA/Keshik rushes is to have a decent chance to survive, not to commit suicide.
One can see Iron / Copper even before one has the techs for it. Just press Ctrl + Y and look at the tile-yields, pillage what is above normal.