Depends. But 270-280 grainers get the nod from me.
My "universal" 45 bullet is the NOE 270K mathman mentions, along with an LBT 280 LFN. Both shoot well at popgun speeds in SAA type guns, up to the 25-5 with midrange loads into the Colt Anaconda all the way to the brutish Ruger Redhawk and Bisley 454 Casull. At around the 1,000 fps mark, they are well suited to a wide range of guns and sight limits.
As mentioned, the 270K is essentially a WFN meplat with similar attributes to the RCBS 270 SAA. It fits in the SAA length cylinder and is a bit more suited to the 45 Colt than the Lyman 454424, which Elmer had an imposed weight limit when he created it. The NOE 270K also drops a .455 bullet with wheelweight metal, something the RCBS 270 SAA doesn't always do. It's needed to do best work in the 25-5 and Anacondas and some SAA's or older Rugers.
As good as they are, the .455 LBT 280 shoots a trifle better once ranges go to 100 and beyond; anyone who has used the old 454190 Lyman in a 45 Colt will tell you how flat accurate that bullet is. The LBT 280 LFN is that shape with a better killing profile. Nose first sized, it goes down to .451 and still stays balanced without misaligning.
The 300's and beyond are more specialty bullets; they have their place and more limited platforms, but are generally more horsepower than most people need for a day to day gun. Not that they can't do it. Sight regulation in some guns gets iffy unless top velocities are used.
