I believe it depends more on the quality of the bullet and the accuracy it provides out of your gun. All three will effectively take a Whitetail, however, they must hit home with accuracy.
Find the sabot / bullet combo that shoots well and hunt with confidence.
Good advice here.
Something to keep in mind though. Velocity decreases in flight, mass doesnt.
I hunt pretty much exclusivly with ML. I guess 180 grain up through 490 grain projectiles... it all works if you hit them in right. Its a large target too.
one of my guns really likes 80 grains 777 + 460 grain .451 caliber bullet. Another loves 90 grains powder pushing a 40 caliber 250 grain spitzer. The musket likes roundballs.
As it stands now, all of my projectiles are full lead, non-jacketed. I let the gun decide what it likes most.
I'd avoid the lightest for caliber bullets (180-200 grain .429's for a .50) if you are merely chasing speed, as I feel at this velocity range heavy lead is more consistent. But if thats what you r gun shoots best, go for it.