The big issue for the Keith fans seems to be authenticity. Like TomAM says, the full diameter front band was a major component, as was a substantial rear band and a big, square lube groove.
The problem with a lot of the Lymans is they reduced the front band diameter for easier fitting across a wider range of guns - and you don't know what you're getting until you measure its output. I don't know if it crept into the 429421, since that bullet has a massive cult following that would complain, but a some of the other Keith designs ended up with rounded lube grooves for easier casting. Keith was big on lube capacity, but in truth, if you have good fit to the gun and good lube, his bullet packs more than is needed.
Accurate has the dual advantage of giving you the blueprint (the 43-250J claims to be the baby), AND allowing you to tweak the blueprint to suit your gun and alloy. I am not a powder coater and know little of the quirks of that process, but the ability to adjust the diameter of the mold's output to account for your "paint" may have some advantages. If not Accurate, then at least go for a mold company that provides you with a blueprint of what you SHOULD be getting.
Many of us have moved on to WFN/LFN designs, and I'm personally a fan of tumble lube grooves for speeding up production. There's a lot of good .44 slugs out there and we can debate them endlessly, but much like a .30-06, a quality Keith SWC is never a mistake, and if you gotta have "Elmer's bullet", it's easily understood.