9mm hasn't won anything. In today's market with today's options it's a good choice. Maybe even the best choice, but when I read the OP I took it to mean that the 9mm Wunderkugel would not be available. Without modern hollow points the 9mm goes back to what it always was,......a really mediocre noise maker. Back to through-n-through, no energy transfer pinpricks. So it's time to go back to what worked before.
And frankly, that's not a FMJ roundnose of any caliber smaller than 12ga. What has been found to work is a large(r) caliber heavy cast bullet with sharp cutting shoulder and a flat point. You get penetration. You get tissue disruption though cutting and you get some shock from the flat front. With that style of bullet would there be a huge difference between 9mm, 10mm and .44/.45? Doubt it, but when working with cast bullets there's an advantage to loading the larger calibers. The lighter bullets in 9mm allow higher velocities which are better avoided. More weight/less speed works better. Also the straight pistol cases like the .45ACP, .40S&W and all of the revolver cartridges are better suited to lead bullets. The tapered 9mm frankly sucks at the loading bench. Take all of that into account and my choice is still the .40S&W for an almost perfect combination of size/weight/velocity, bullet style and loadability. Good combination of capacity and carryability. Doesn't hurt that it's out of favor and cheap on the market. Good guns at half the price of the 9mm model and reloadable .40S&W brass is almost free.
And frankly, that's not a FMJ roundnose of any caliber smaller than 12ga. What has been found to work is a large(r) caliber heavy cast bullet with sharp cutting shoulder and a flat point. You get penetration. You get tissue disruption though cutting and you get some shock from the flat front. With that style of bullet would there be a huge difference between 9mm, 10mm and .44/.45? Doubt it, but when working with cast bullets there's an advantage to loading the larger calibers. The lighter bullets in 9mm allow higher velocities which are better avoided. More weight/less speed works better. Also the straight pistol cases like the .45ACP, .40S&W and all of the revolver cartridges are better suited to lead bullets. The tapered 9mm frankly sucks at the loading bench. Take all of that into account and my choice is still the .40S&W for an almost perfect combination of size/weight/velocity, bullet style and loadability. Good combination of capacity and carryability. Doesn't hurt that it's out of favor and cheap on the market. Good guns at half the price of the 9mm model and reloadable .40S&W brass is almost free.