What should be kept in mind when comparing the relative merits of lead core bullets to mono-metals, is that mono-metal bullets are designed backwards. Looking back to the advent of smokeless powder, when the earliest copper jacketed bullets began to appear, the weight of the bullet was determined by the length of it's lead core. Over time various techniques were employed to prevent core separation, beginning with harder lead alloys which expanded more slowly, then tapered jackets were introduced to control the rate of expansion, followed by various core locking devices, finally to single core bonded bullets like Nosler's Accubond, dual core bonded bullets like the hugely successful Swift A Frames, and the solid shank bonded bullets like those from Rhino. When these bullets were made in different weights within caliber, it was the length of the core that changed to accommodate the desired weight.
A style of bullet that I'm very fond of is the solid shank bonded bullet. Typically these bullets are made with a pure lead core located up front of the solid copper shank, and surrounded by a pleated jacket, which opens in 4 petals not unlike a TSX. Thus when the bullet expands, provided enough target density is encountered, it can open to the full length of the core, resulting in a huge frontal area. The bonding prevents separation, thus a larger frontal area is realized, and the terminal performance is all out of proportion with what has been expected from other bullets within caliber. The expansion cannot extend below the core into the shank, so gyroscopic stability is maintained. Thus we see that core length can have a direct affect on terminal performance beyond just enhanced penetration due to the greater momentum of a heavier bullet.
Enter the mono-metals. These bullets were more of a departure from the traditional lead core bullet than was obvious at first glance. All of the hollow points within caliber are approximately the same depth, so within caliber the expanded frontal area is fixed. This isn't a bad idea, but it is different. The advantage is that the bullet cannot over expand, regardless of the impact velocity or the bullet weight, making the mono-metals an excellent choice for dangerous game at blood on the shoes ranges where impact velocities are very high. The fact that the bullet cannot over-expand is important to stability, because a bullet needs a longitudinal axis to rotate around if stability is to be maintained. A bullet that expands right down to it's base is less stable than one which has a third of it's length remaining behind the expanded nose section, that is the bullet shank. The way to adjust the weight of a mono-metal bullet, is by adjusting the length of the shank rather than the length of the expandable nose. So while the nose depth of all bullets weights within caliber are very similar, the shank length varies significantly between weights. As we see, there are lots of ways to skin a cat.