CC, you need to look at the rifles, online or up close and personal, to know what makes one better for your purposes than the other.
The first thing you need to look at is the throat and bore condition. Many of these rifles were commercially sporterised from NOS rifles, many were converted by Bubba with lackluster results and many were shot with "corrosive ammunition" and not properly cleaned afterwards, which left the bores badly pitted or corroded.
If you come across a rifle which has a very dirty bore and you can't see the metal, pass on it. It's very easy to pick one up with "frosty, pitted, corroded bores" which are covered up by the fouling.
If the deal is too good to be true, be wary.
Which sight system do you prefer? Diopter or Tangental? Some folks just can't get used to the Diopter type, or won't/can't learn how to use them
Now, you need to look at the bedding, which usually isn't an option. There is one test which is quite easy to do, squeeze the forestock at the end or wiggle it up and down to see if you can feel any play at the receiver. If it's moving around, accuracy won't be good until its bedding issues have been addressed.
No 4 rifles are a bit more prone to such issues than No 1 rifles if the No 1 rifle still retains its forearm bedding ring/screw/spacer.
These rifles were designed to have appx 6 pounds of upward pressure, four inches back from the muzzle. When the fore-end tips are cut off, there is no longer any pressure applied. This may or may not have an effect on accuracy. If the bedding is very tight, you can usually get away with it.
You're going to get a lot of "headspace" comments. These rifles were all purposely manufactured with "generous" chambers and headspace so they would be able to load and fire slightly dented, dirty, or slightly out-of-spec ammo. The very odd one will have a "tight" chamber but they're unicorns.
Check the stock line for rust pits. Some of these rifles will be deeply pitted below the stock line.
The finish may be worn but not affect function or accuracy. Most of the rifles we see were Factory Thorough Repaired somewhere along the way to being surplussed.
Expect to see what most would consider excessive case expansion after firing. It's normal.
One last thing, these rifles were considered to be acceptably accurate if they shot FOUR INCH (9cm) groups, with issue ammunition, at 100 YDS.
Check the safeties to make sure they work. Check the magazine to make sure the floor plate and spring are functional and the bullet retaining ears are still there or not visibly damaged. Magazines are expensive to replace.
This should get you started, so you have an idea of what to look for.
I no longer purchase any mark of 303 British rifles online. Bubba has had to much of a hand on many of them, and I end up with "parts guns" which are often worth less than what I paid.