I have seen quite a few debates about random drops versus tokenization. Should bosses have a 2% chance to drop the Ubersword of Epicness or should they drop 2 badges (and a vendor in town exchanges the Ubersword for 100 badges)? There are merits in each direction, although I tend to favor tokenization because random drops tend to encourage endless grinding of a single dungeon/boss.
Let me, as I often do, mention a third-way solution used in City of Heroes (and a fourth). City of Heroes has used both, but the most sought after items (purple crafting recipes) are random drops from a shared loot table. CoX applies it even to trash mobs, but you could restrict it to bosses and let all of them have a chance to drop all the rare items. That would be an even larger lottery, but you would not have only one boss in the game that dropped the one item you want. Of course, players might replicate “grind one dungeon endlessly” by optimizing for the most time-efficient dungeon, but I am not in the mood to ponder people who want to spend their $15/month doing something they do not consider fun (if you like grinding the efficient dungeon, hey, double-win for you). OTOH, I can understand why you might prefer fewer rolls with higher chances to many rolls with a lower chance of that specific item.
Several games use a menu as a middle-ground between drops and tokens. When you win, you pick one item from a short list. WAR chests are a good example. Another implementation is to give a token that can be redeemed for one of several items, rather than tokens you accumulate as currency. CoX combines menus with randomness by including “a random pick from pool D” as an option on the prize menu. Another middle ground is to have a fixed drop that is variable by class, usually done as a barter item that some or all classes can trade in for their equivalent of the item.
My thought is that players want both fixed and random elements in their game rewards. They want to know that they are going to get something, and little nuggets of achievement are encouraging, but they also want some chance to hit it big. Slot machines make a lot of money, and developers can embrace that without making everything random.