It's a tough choice to make - premium boxes are nowhere near as value for money as the previous gold boxes were. I've taken the plunge on a quite a few of them this last week or so and 8-9 times out of 10 the result was disappointing (read 2 epics). I had a crapload of legacy items to burn for boost so I used most of my tokens on gold. On the other hand, as others have mentioned the really good items can only be found as legendaries from premium boxes.
In a nutshell, it kind of depends on your priorities and situation (say you're way overloaded with legacy items). If you're not in that much of a hurry to get those legendary only items, gold could be the better option right now.