Of those three words, only decolourised carries a real meaning. It means the juice has been filtered, usually through activated carbon, to strip out colour and unwanted compounds after whole-leaf processing. Filtered and purified describe that something was done, without telling you what, or to what standard.
​That matters more than it sounds, because decolourised is the word regulators themselves draw a line around.

The International Agency for Research on Cancer classifies non-decolourised whole leaf extract of aloe vera as possibly carcinogenic to humans, Group 2B, on the basis of sufficient evidence in animal studies. California lists that same ingredient under Proposition 65.
Read the wording carefully, because the wording is the whole point. That classification applies to non-decolourised whole leaf extract. It does not apply to inner leaf gel, and it does not apply to decolourised products, which is what commercial aloe drinks generally are. The US National Center for Complementary and Integrative Health makes the same distinction.
​So decolourised on a label is a good sign rather than a suspicious one. It is the step that addresses the thing the classification is about.

Filtered, purified, triple-filtered, pure. None of these is a defined processing term for aloe. They tell you a step happened without telling you which step, or against what standard, or whether it did the thing that actually matters.
That does not make them dishonest. It makes them uninformative, which is a different problem and an easier one to handle: treat them as neutral and keep looking.
​So the check is short. Look for either inner leaf or decolourised somewhere on the pack. If it says neither, assume non-decolourised whole leaf and treat the aloin question as open. I sell aloe and earn a margin on it, and I would rather you apply that test to my products than take my word for them.

If you want the most aloe, pick the plain Aloe Vera Gel at 99.7% inner leaf. If you suspect you will not finish the plain one, pick a flavoured version instead, because a drink you actually get through beats a purer one you abandon after a week.
​The trade-off is exact, and it is printed on every pack: the better it tastes, the less aloe is in the bottle.

Ranked by how much aloe is actually in the bottle:
Aloe Vera Gel, 99.7% inner leaf. The plain one, nothing added.
Berry Nectar, 91%, with cranberry and apple.
Mango, 85.8%.
Peaches, 84%.
​That ladder is the thing nobody selling these mentions, and it is not hidden: the percentage is printed on every pack because it has to be. The roughly nine to sixteen points of difference go to fruit concentrate.

The plain gel suits you if you want the most aloe per serve and you are willing to meet it halfway. It is bitter and slightly vegetal, and cold helps more than anything else: straight from the fridge, in a small glass. Most people who tell me they gave up were drinking it warm.
Berry Nectar is where most people start, and at 91% you are giving up very little. Mango and Peaches are the sweetest and the lowest in aloe, and if that is what gets a glass into you each day, that is a reasonable trade rather than a compromise.
​None of these numbers is bad. The point is only that you should know which one you are choosing, and the percentage is printed on every pack so you can. I earn a margin on orders through my link, which is why the number, not my recommendation, is what I would go on.

It means that of everything that went into the bottle, 99.7% by weight was aloe vera inner leaf. The remaining 0.3% is the stabiliser and preservative system, and the number is printed there because Australian food law requires it, not because the brand chose to be generous.
​That second part is what most people miss, and it changes how much credit a high number actually deserves.

Because Standard 1.2.10 of the Australia New Zealand Food Standards Code requires it. Where an ingredient is named in the product name, or a buyer would reasonably associate it with the product, the percentage of that ingredient has to be declared. Aloe vera in something called Aloe Vera Gel is about as characterising as an ingredient gets.
​There is no minimum threshold. A drink with 2% aloe has to print 2% just as plainly as one with 99.7% does. That is the useful part: the number is not a boast the brand opted into, it is a disclosure it could not avoid.

Almost everything that matters. The percentage is a quantity, not a quality, and four things it stays silent on are the four things worth knowing.
It does not say which part of the leaf you are drinking. Inner leaf and whole leaf can both be 99.7%. It does not say whether the aloe was pressed from fresh leaf or reconstituted from powder, and both can be 99.7%. It does not say what the aloin level is. And it does not say how long the leaf sat between cutting and processing, which is most of what separates one bottle from another.
​Two products can print the same number and be meaningfully different products. That is not a loophole, it is just the limit of what one figure can carry.

Turn the bottle around and read three things in order. First, the percentage. Second, where aloe sits in the ingredients list, because ingredients are listed in descending order by weight and the first one is the largest part of the bottle. Third, whether the pack says inner leaf or whole leaf anywhere at all.
If the percentage is high but the pack will not tell you which part of the leaf it came from, the number is doing public relations work rather than informing you. A brand confident about its processing says so.
​For what it is worth on my own range: Aloe Vera Gel is 99.7% inner leaf, Berry Nectar 91%, Mango 85.8% and Peaches 84%, with the difference going to fruit concentrate. I earn a margin when you buy through my link, which is exactly why the method above is written to work on any brand's label, including the ones I have no relationship with.