Assuming no sp appreciation then yeah heads are best. BUTIf ARV...

Assuming no sp appreciation then yeah heads are best. BUT

If ARV goes to 12c, your 2c oppies are now worth 7c (assuming they don't continue to trade at a premium)... Almost 4x return

If ARV goes to 12c, your 6c heads show a 2x return.

If you believe the company has excellent prospects and that its seriously undervalued, then oppies are your best bet for maximum leverage... And I'm assuming you invest in ARV for the appreciation in sp you think it will give you, as there's no dividends in the near future. No brainer to me, but each to their own (leverage does work both ways)