In regards to handgun cartridges, trying to decide whether a JHP of FMJ is more effective against a human target is like arguing about the proper pronouncement of the word 'tomato'. One way is right for some people the other way is right for others. In the great scheme of bullet effectiveness, handgun cartridges (both FMJs and JHPs) are relatively ineffective. Handgun projectiles simply do not posses enough power to reliably incapacitate a human target. If you want to hurt somebody hit ’em with a rifle cartridge.
I know this will probably ruffle allot of peoples feathers but with handgun bullets energy means nothing. The only reliable wounding mechanisms are penetration and projectile diameter. Handgun bullets don’t posses the required velocity to wound through the transfer of energy. However, both penetration and projectile diameter are inconsequential if the bullet doesn’t get put in the right place. The reports put out by Evan Marshall, although definitely useful, should be looked at with a close eye. Too many variables are left to chance and no two shootings are alike. So even trying to compare 2 shootings with the same load can give vastly different results. Allot of the 'one stop shot' effectiveness has to do with the target. Is he a high dedication individual absolutely set on completing his task? Is he high on drugs or alcohol? Is he predisposed to stopping because of being shot no matter what the caliber? Allot of things are left to chance.
Additionally, the definition of ‘one shot stop’ as used in Marshals reports is frequently up for debate. Just because the target stops doesn’t mean he is not a viable threat or incapable of staying in the fight. One may stop because they have programmed them self to think "if I’m shot it’s all over" and will just give up. The fact of the matter is if the target falls to the ground and stops fighting after one shot but is still capable of doing harm to me he is still a threat. The bullet didn’t necessarily stop him his lack of dedication may have had just as large of a role in his falling down and giving up. Never the less, Marshall did have to have a starting point so I guess his decision is a good as any. My point is not to put too much faith in any reports whether they by from the FBI or Marshall or any other. Statistics are just information gathered and tabulated. They are a good reference point but not something to put all your stock in.
Choose a bullet that you have personally tested and know is correct for your environment. Make sure it functions in your gun and will perform reliably in every aspect. Feeding reliability, accuracy, penetration, expansion, etc. If it’s a JHP that fits your requirements, great use it with confidence. If it turns out an FMJ is better for you and your circumstances, super. Neither one gives you a significant advantage over the other; they are both just as ineffective.