YOU have to find out YOURSELF what works best for YOU.
But, if you still want to hear my opinion ...
I will always look at the solution. Sometimes I can't find it myself, sometimes I am not quite sure and even if I am sure that I am right, it gives me satisfaction to see 'my' solution printed. (And sometimes I am sure that I am right and it turns out I am not.
)Or to put it differently:
Some people ask about the right time to do cardio - before or after the workout, in the morning or in the evening. Correct answer: the best time is the time when you will actually do it.
That means for Tsumego: It is by far more important that you actually do it than whether or not you look at the answers.