I'm no expert, but I think the bevel base is to make easier to seat the bullet. From what I've read, the tradeoff is a little less accuracy and more leading.
Google "Leadheads Bullets"; I can't cut and paste the web address for some reason.
Model PM44-250 is the plain base Keith style. I have ordered from them before and it is a good product.
Accuracy of both styles has been comparable for me. To mitigate leading in the BB style, I have applied a little Lyman moly lube around the circumference of the case mouth prior to bullet seating; this seems to serve as a gas check of sorts and provides some additional lube as well. Dipping them to just below the crimp groove in Lee liquid alox and setting aside to dry seems to work just as well.
A friend and I have compared meticulously-hand-cast flat base bullets with Valiant bevel-base bullets at distances out to 200 yards in our 624s, 629s, and Ruger Flattop 44 Specials and can determine no appreciable difference in accuracy between the two.
I'm with Sunday Bill. I load and shoot several different calibers and sometimes use flat base and sometimes bevel base. At typical handgun ranges, I doubt anyone can tell the difference. Have not seen any difference in leading or not either.
It is almost sacrilige to some but I LIKE bevel bases. They are easier to seat, self centering as they enter the case mouth and, usually quite accurate.
It's been my experience the only difference between a BB bullet and FB bullet is the BB bullet is easier to seat, nothing else. That's just my opinion...
All I can say is that I've been using bevel based cast lead bullets in both handguns and rifles since about 1980. Accuracy has never been a problem. One of my very best match loads for my 1903 rifle uses a bevel based 165 gr. Flat Nosed bullet. I do carefully examine base of each bullet before loading, culling any bullet that is not perfect.
I don't care for bb bullets as they make a mess in the lubesizer. If you are buying them lubed it would take a master level shooter to tell any difference.
IMHO fitting the bullet diameter to the chamber throat diameter
is the most important step in obtaining accuracy and reducing
leading. Bullet style should not affect this. I have never used
the FB cast bullets even if it does make Elmer roll over in his grave.