Here's half your answer [img]/images/graemlins/smile.gif[/img] :
Wizard of Odds--Match the Dealer side-bet
It should be trivial to figure out the other part. For these side bets, the more decks, the less the house advantage. However, the more decks the worse the bj game will become for you. Also, as the edge on the "totals" bet increases (due to excess small cards to be dealt), the worse your bj bet becomes.
Are you allowed to bet more on the side bet than on the bj bet?