It is a personal preference =p I usually recommend thinking about what the final lineup you want is and going towards that. The reasoning is because you want to maximize the efficiency of your use in resources. For example, do you know if your final lineup will include Tobirama [Edo Tensei] or Minato [Edo Tensei]? Are you asking because you are just collecting? Why are you picking between the two? There are many details that could affect what your "best choice" is.

If I had to choose based purely on the comparison between Minato [Edo Tensei] and Tobirama [Edo Tensei] and based on how I would make a lineup, I would probably choose Minato if I HAD to choose between the two.

However, the biggest question is. What do you need it for? What is your final lineup going to be? How does your resources look? What lineups do the other players on your server or cross-server use? Do you have a lot of available resources or are you saving up? Usually after answering those questions, among the many other possible questions, you will be able to find the right choice for you =p

TLDR: If I had to choose between the two and I was not given the choice of saving my resources, I would choose Minato [Edo Tensei].
Remember, coupon/ingots do not generally depreciate in value over time. So saving is never a bad option.

okay tysm :D