Well, first, I believe that meplat just refers to the diameter of the nose. So a WC>SWC>"flat-nosed" jacketed, in terms of size of meplat.
But I think the key here is that expansion is far more important than the initial size of the cut entering game. If there were no expansion, then sure a hardcast SWC would be slightly more likely to nick and thus take out a large artery or vein at the edges than a "flat-nosed". But the flat-nose will have expanded more than a hardcast SWC, but expanded less than a soft-cast SWC.
So I think the bottom line is, getting a large degree of expansion while retaining adequate penetration is far more important than initial shape of the bullet. Which is itself a function of *matching* MV to the bullet. That's not to say that the shape isn't important. It is. And the meplat size is important. The wider the better, all other things being equal. But not because it pokes through wider all way; rather, it's because the large meplat *initiates* the rapid expansion and ultimately large expansion.
So if you're talking about a really low velocity such as sub-1500 fps, then a soft SWC is going to expand more than a flatnosed jacketed bullet, and even a "semi-hard" lead SWC will expand more. But if you're talking about higher velocity, then it should be "roughly the same" but with the jacketed bullet having advantage of less lead fouling. Because once you get the velocity high enough, they'll both expand to the maximum, which will be the same amount, roughly.
I suppose if all other things are equal, and it's a given that "significant expansion" will occur from either, then the SWC (if not too hard) has the edge on terminal performance, simply because the slightly-wider meplat initiates expansion faster and results in ultimately greater expansion. But then again, if your vels are *really* high, and/or if the game is super tough and large, then jacketed bullet would have the preference because the jacket will help hold the bullet together, and in that scenario, LESS expansion is better, not more.
Bottom line, my guess is, it depends upon velocity:
Under 1500 fps=> the SWC
1500-2000 fps=> the SWC on most game, still (but matching hardness to game toughness)
2000 and up=> the flat nose, due to both lead fouling issue, and better penetration but "still-good-enough" expansion.