I doubt you would notice any measurable difference in the slightly lower BC of a similar weight 458. You gain the advantage of "closer to bore" sizing and rifle bullet construction vs a pistol bullet. The majority of 458s we would use in a ML are made for 45/70 speeds which are a great match for ML speeds.

In the 458s, i shoot the Barnes 300gr SOCOM which is made for roughly 1900fps MV, the 325gr FTX which is loaded upto 2300fps by Hornady and the Lehigh 275gr which probably will perform best at impacts of 1400fps or higher. The SOCOM and big FTX have BCs of .230 or more if that matters. I like them mainly because they shoot very well for me and have plenty of knock down for any game i currently hunt. Plus i get the FTXs really cheap from a local supplier.

I got 100 of the 458-275gr Lehighs recently so they are going to get a better workout. I only had some sample packs before and no option for shooting them faster than common ML speeds.