They should not decide it equally, and the work of this page is to say which of them earns a vote. Nine pages sit behind this one, each following a single variable, and the pattern that emerges from them is clearer than any individual page can be. Two of these five variables reverse the answer. Two of them scale it. One of them is not a variable at all, and a sixth that readers keep adding has nothing published behind it. Variable one: passive or adjustable release. This is the shape of the decision rather than an input to it. A hanging 12ml car perfume is a bottle with a wick and an exposed liquid surface, releasing continuously at a rate set by temperature and airflow, indifferent to whether the cabin holds one person or seven, until the bottle is dry. SOSA Safar atomises pure undiluted oil cold from a closed bottle - no water, no heat, no residue - only while running, with three speed settings and an auto shut-off timer at one, two or three hours, up to ten hours continuous or thirty hours intermittent per charge, 2000 mAh over Type-C, cordless, about 9 cm so it stands in a cup-holder, and a 20ml bottle in the box. Those are not two tiers of one product, and spending more does not buy a better version of continuous presence - on that axis the device scores lower, because it produces nothing while off. That is the whole argument of the anti-upgrade page. Variable two: passenger variation. This flips the answer, and it is the strongest single input in the family. Count the correct levels in your week. A vehicle carrying the same two people on the same kind of journey has one, and once you have found it with a well-chosen composition placed away from the driver, there is nothing left for a dial to do. A vehicle that is a solo commute on weekdays and a full cabin at weekends has two, and a fixed output cannot hold two at any price - so the reader is not choosing between cheap and expensive, they are choosing between a format that can answer their question and one that cannot. The rule underneath it is that the level belongs to the most sensitive regular passenger, judged from the back row in their first minute aboard, because the driver sits nearest the source and has already adapted - receptors stop reporting a stimulus that does not change. Variable three: willingness to maintain something. This also flips the answer, in the opposite direction, and it is the one readers most often get wrong about themselves. Write the two lists out. Hanging: buy a 15ml refill at ₹399 to ₹449 when the level drops, and that is the whole list. Powered: keep it charged, and buy oil at ₹1,049 or ₹1,099 per 100 gm. The failure modes are not symmetrical either: a bottle declines slowly and in plain sight, while a flat battery is sudden, silent and leaves the cabin with nothing at all. Features you will not touch are not benefits, and a capability bought with a habit you will not keep is worse than no capability. Variable four: driving frequency. This scales the answer without reversing it, and the distinction matters. A passive unit is billed by the calendar: it evaporates whether you drive or not, so a vehicle used twice a week consumes it at roughly the rate of one used daily. A device is billed by the journey: it produces nothing while off, so its value divides by your occupied hours. High hours therefore make the device used rather than owned - but they do not make it necessary. Twenty occupied hours a week with one stable set of passengers still has one correct level, and a bottle serves it. The hours page works the division through; it is hours multiplied by variation that justifies ₹3,999, never hours alone. Variable five: budget. This follows the other four rather than leading them. The gap is real - ₹449 to ₹509 against ₹3,999 or ₹4,499 - and the instinct is to treat the cheaper purchase as the safe one. It is not symmetrically safe. A reader whose cabin genuinely needs the level changed every week and who buys a ₹479 bottle to be sensible will take it out of the vehicle within a month because somebody keeps asking for less, and the money is simply gone. The expensive mistake and the economical mistake are the same mistake: spending against the wrong question. And the sixth variable, which readers keep adding and which cannot carry any weight: cabin size. SOSA publishes no coverage figure for Safar at all - a full sweep of the product page returns nothing for square feet, cubic metres, seat count or room size - so nothing here sizes it to a vehicle. A larger cabin wants the source moved rather than the dose raised, identically for both formats: distance does the work and the ventilation is the only transport. One more input that appears on no list of variables and settles more purchases than three of them together: scent availability. The waterless refill range holds fifteen scents across two tiers and contains no oud and no lavender. The 12ml range contains both - oud at ₹509 with a ₹449 refill, lavender at ₹479 with a ₹429 refill. A reader who has decided they want oud in a vehicle has decided this entire comparison before any of the five variables is consulted. Check that first; it takes a minute.