I won't say coated bullets are more accurate than lubed bullets. But I will say it's easier to find accurate loads with coated bullets than it is with lubed bullets.
Lubed bullets:
You hit the loud button and bang, the bullets off to the races. The base of the bullet compresses hydraulically pushing the lube outward and forward in front of the front drive band/bands sealing and coating the bbl. This is where the fit/allow/lube/pressure (powder) combo's come into play. Get everything right and you have an accurate load.
Coated bullets:
The lube is already there so it takes the finding of the correct pressure/alloy combo out of play. Either get the fit part correct or use a soft alloy (8/9bhn for up to 35,000+/-psi loads). All's that's left is matching the load with the bullet and test for accuracy.
I've owned a beater 629 for years & tested a lot of different cast/swaged lead bullets in it. When I 1st got interested in coating bullets I grabbed it an retested cast lubed bullets vs cast coated bullets. The scope of the test was to find plinking loads that would do minute of golfball @ 25yds. MOGB ='s 1& 1/2" groups/nra x-ring @ 25yds. Same dies/brass/powders/cast bullets/shooter/etc. The only difference was 1/2 the bullets were lubed vs pc'd from the same lot/casting session of cast lead bullets. I tested 5 bullets and 7 different powders doing a simple ladder test with each bullet/powder combo. At the end of the day I ended up with 3 vs 13
3 vs 13 is huge!!!! Had 3 lubed loads vs 13 pc'd loads
Both bullets that are coated and lubed can be accurate, it's just easier to find accurate loads with coated bullets.
Man/moment/machine, but in this case it's pc and what it brings to the table. 2 bullets cast from the same time from the same mold using the same alloy (20# pot & a 6-cavity mold). It'a a lee 312-160 tl bullet.
I used a traditional lube (lbt blue) + 1 thin coat of 45/45/10 tumble lube on 1/2 of the bullets and I pc'd the other 1/2. I used a 308w that just got re-barreled and tested some loads with h335. While accuracy wise none of the loads were anything special, it was an eye opener. The traditional lubed bullets were right with the pc'd bullets for the 2400fps & 2500fps loads (34& 35gr loads), the target with 10-shot 100yd groups.
As you can see the lube failed and accuracy went south with the 36 & 37gr loads. I did a 2nd heavy coat of lube on the same bullets and plan on re-testing the 36 & 37 gr loads to see if the groups/accuracy comes back.
The pc'd bullets on the other hand kept getting tighter groups and the load/powder got heavier. The 37gr 2650+fps load did just under 2" for a 10-shot group & 100yds.
I plan on testing 38gr & 39gr loads to see if the groups tighten up any (2800fps range).
This is a good example of the getting the fit/alloy/lube/pressure combo right with lubed bullets compared to pc'd bullets. The velocity of the loads steadily climbed with the pc'd bullets while the lubed bullets started to fail at the 35gr pressure range. Just not enough lube to seal the bbl. The bbl didn't have any leading, the hard 45/45/10 protected it. I've always said bullet lube is a gasket also. And this is a good example of not enough lube and the loss of pressure/velocity.
Anyway just another opinion on what I've found with lubed vs pc'd bullets from a 30+ year bullet caster/swager.
