I don’t know about the scents. Whenever, there is a 5 or 20% of an epic scent, I get it for some odd reason.
So far on these scent strikes I am most likely to get an epic scent, then a scent capsule, then either a rare or large scent. I would much prefer hc because the boosts are very low in quantity, especially speed which is the boost I really need for my ranking in most tourneys.
It would never occur to me to buy coins nor would I advise anyone, but it is true that an HC prize allows you to choose what to spend the prize on.
Anyway, the worst is not so much the prize as the difference in the prizes. 99% will receive miserable tournament prizes and 1% very large prizes. It is of little interest to be fighting a whole weekend when the most you can hope for is 10 boosts or 50,000 coins. In fact, for most people it is much better not to participate in the tournament and to participate in the normal arena by winning coins and incubators to open.
I find that the reward is more valuable when the tournament itself is fun and accessible to people. Winning 10 boosts isn’t worth much if you were in essence locked out by other people with max boosted creatures. If the reward is to be something like bucks or boosts (two very significant resources for increasing the strength of your team), I would prefer they come from skill tournaments, where more people are able to compete and attempt to win the larger prizes.