Before you read this, I am not saying you cant make PRS long range shots with a tikka or a howa or remington with a factory stock and hit targets, I am saying shooter being equal there going to get more consistent shots on target. I am quoting you from your first post
"I want the most potential possible for accuracy when I'm experienced, from my first rifle, so I won't feel the need to replace it quickly". The bravo chassis will get you this and past this since you can upgrade it to make it even better as you progress. As they say on here "
Buy once, cry once" so the best bang for your money not over your price is the bravo chassis IMHO. Anyways I have listed a few reasons why its more accurate along with links to videos explaining what I am talking about as well as My reasons for every thing I want to use in my build. Those reasons are related to accuracy as well.
To answer your question, there are a lot of reason why the factory stocks are junk compared to the KRG Bravo and any other after market stock. The KRG has an aluminum rail that runs from above the trigger to the end of the stock (black piece on the green or tan stock in pictures). The factory stocks are all plastic with metal lugs mounted in them. The factory stock will flex when you put load on it with a bi-pod, while the KRG is very very minimal to no flex at all. Accuracy is getting a consistent shot every time, if your rifle is flexing differently every time you load up the bi-pods then recoil will be different ect. There is also a good chance that the factory stock will touch and push on the barrel. The barrel needs to free float from the action to the end of the stock. There is a harmonic sound wave that travels down the barrel. If that is messed with that can throw a longer shot off alone or give you erratic bullet patterns . At long ranges millimeters turn into inches and feet. meaning you can be off center by 3mm at 100 yards but miss by inches or feet at 800 yards. Here is a video under 10 minutes that explains harmonics.
You can add stuff later on as you need it, to help with your accuracy in positions you will be shooting in PRS matches, there are all kinds of positions they have you shooting in, sitting, kneeling, prone, off barricades, threw holes ect ect. With the upgrades you get a better position on the gun and the buttstock with fully adjustable ones like I have linked bellow. lastly if all these did not help with accuracy then there would be no aftermarket chassis since the factory stocks would be good enough and the pros wouldnt be using them. Even the KRG has a fully adjustable shoulder rest you can add to it later on if you feel you need it. The more expensive chassis are all aluminum, foldable buttstocks ( you can get an upgrade for the bravo if you wanted, linked below.
https://kineticresearchgroup.com/product/tool-less-pad/
That stock is meant to be upgraded, you can also later on order this then it will be a 1500 stock.
https://kineticresearchgroup.com/product/trg-stock/.
Short video from Brownells on the bravo chassis if you want, less then 3 minutes long. Shows the aluminum rail nicely.
Even though this video is about the sniper hide rifle, it applies to all after market chassis to include the bravo, but the bravo just doesnt have as many options out of the box. My last reason it makes you more accurate of a shooter.
This Special Edition SABER M700 is a uniquely designed precision rifle inspired by Frank Galli, former USMC Scout Sniper.
www.ashburyprecisionordnance.net
The rest if you want to read it is why I also choose not to buy a rifle and choose what I chose.
Trued or bluprinted actions, read up on it and how it affects the barrel ect. That is why I am going with an aftermarket action vs a tikka or Howa, i dont want to buy a tikka at 1k then later on spend anywhere from 150 to 250ish to have my action trued later on. Then your rifle is down for a week or so depending on if gunsmith is local or you send it out. Anyways I digress, the barrel from factory rifles do not sit straight off the actions, some may but a lot dont, its a crap shoot when you buy a stock rifle. That affects how the bullet loads and travels down the barrel and harmonics. This under 10 minute video explains this as well and shows you how far off it can be from the factory. This is with all rifles from factory to include Howa, Tikka, Remington ect ect.
Trigger and trigger squeeze can affect your shot as well. With the ELF 700 I can adjust the trigger down to around 2 ounces all the way up to 5 pounds, again if you pull on the trigger and its not light enough then you can pull the barrel left or right and throw your shots off. Soo I am opting to go with the trigger I have choosen to go with, plus with that trigger you get a curved or flat finger trigger. That trigger is also adjustable up and down so you can make the trigger fit you.