I'm hoping Mike (Wolfplace) will jump in here with his opinions, but till then, I'll offer this.
The good old GM Delco-Moraine "400" bearing was an aluminum bi-metal bearing, and that bearing was widely used in the '60s and '70s. I used the hell out of them myself in 396/427 hi-po Big Blocks, and they held up very well for me.
The "400" bearing was quite a bit harder that a babbitt-overlay tri-metal bearing. The aluminum construction didn't allow much embeddability if you got a little crud between the crank and bearing. But, the factory hi-po forged steel cranks we were using back then were Tufftrided from the factory, which left a VERY hard surface.So, the hard bearing didn't beat up the crank surface too much because the bearing, even though it was harder, was much softer than the crank surface. But, you needed to be sure to maintain a CLEAN oil supply, and block off the filter bypass.
Now, when I rebuilt one of those engines, if I had to have the crank turned I'd use a tri-metal beearing because the turning removed the very thin Tufftriding layer and exposed the softer material underneath. Or else, I'd have the crank re-nitrided after turning and go back with the DM "400" bearings, just depending on the application.
I've run the old FM AP-series bearings in my 455 Olds engines as recently as the early '90s. Even using them on reground cast cranks, they worked very well for me. Alot of guys didn't like running them on reground cast cranks, but I put over 1100 passes on my last 455 Olds race engine before I sold it to a street guy. It held up fine for 2 more years, until his car got stolen.
The aluminum bearings are just not as forgiving of dirt or easy on the crank as babbitt-overlay bearings. But, IMHO, they're "tougher" than a tri-metal bearing. So, take steps to insure a clean oil supply at all times, which you should do anyway.
Mike, feel free to jump in here and correct me if you feel it's necessary!