I did some very rough math (that is, I didn't account for crits, and only tested a 60% chance to hit, or compared to the Fighter's 4th attack, results may skew when you account for those) but they're equal if you double the damage for two attacks (presumably doubling the damage modifiers as well), and roughly equal if you triple the damage to account for three attacks.
However, while they're roughly equal in overall damage at 2-3 attacks, the second attack means that you only have a 1/9 chance of not dealing any damage whatsoever. This drops to a 1/27 chance with a third attack. This is a pretty dramatic difference in feel, to have a low to no chance of completely whiffing.
Whether you like the feeling of "One strike Will topple anything!" or "My individual attacks don't do much, but I do enough that I'll at least deal some damage this round," is up to the player. Personally, I like the latter, especially as it's flexible enough to switch between fighting multiple weak opponents or a single tough foe.