Here we go again
First, let me say that in positive rounds, I go to two hands myself (or even three).In case other players join the table it's clearly better and it's less showy than putting the whole money on one spot.
In the course of a discussion here about the speed issue some years ago, I decided to make an extensive test.I found that there was practically no time gain playing multiple hands. Alone against skilled dealers, it took me on average 6 minutes to deplete a normally cut shoe, no matter how many hands I played.
There is of course one great argument for multiple hands and that's at the end of the shoe when the cut card is bound to come out. Here the card eating is actually in the player's favor because it allows deeper penetration.
Francis Salmon