It also depends on what you are looking for in a game. Do you want a fun quick game for fun (where Impetus would work), a more complex tactical game (Field of Glory?) or something historically accurate? Do you want to play only historical match-ups, or do you want to see what happens when the Romans go up against the Egyptian chariots? Are you open to other games (such as Warmaster Ancients)?

In London at the CLWC we use FoG, Warmaster Ancients and DBMM. I think you might still get a game or two of DBM if it took your fancy. All have their adherents though I do not think any of them major on Strategy & Tactics, rather they tend to favour the formations using the right tactics against the appropriate enemy.

I have tried Impetus and would not play it again, the reason is that it is horribly luck dependant and so that does not cut it for me. Chance yes, has to be there but frequent extreme chances, no thanks.

Ok, here are my preferences:

1) A fun game
2) Fairly historically accurate. It doesn't have to be perfect, but I would like it to convey historical themes. I'm also fine with "what if" scenarios, like Persians vs Romans, but not something too far-fetched like Normans vs Egyptians.
3) A cogent tactical system. I would like strategy and tactics to play a major role.

To hit a flank, starting in front of a unit, you would have to make two moves of course (each requiring passing a leadership check). One move to get round the flank and the other to charge. It can happen but also it can fail. Yes I would expect infantry to be outmanoeuvred by cavalry.