You pick one version and test it. A test says more than a thousand theories, so just keep going.
The Snowflake Method is an iterative method where you're allowed/encouraged to go back and "fix" things after each step. You're even encouraged to go back and adjust the Snowflake after you've written about halfway into the actual first draft.
Pick the one version that feels best now, keep the rest in a separate document and keep going.
You may get stuck and then you know that version isn't working, so you go back and change things around a bit to make it work or to adjust what you've done to fit the next variant you want to try.
That's ok. That's why you're doing a Snowflake instead of just typing away at the draft. You see the problems and the options now and you can, by taking a smaller step than a whole draft, test them.
It may also turn out you have several different stories with a common theme (perhaps an anthology?) Then you start with the one you like best.
Your characters are most likely going to be good for any of the other versions as well. After all, at this point, you've done two out of 10 steps.
And trust me, it's hardly 20% of the job done. The amount of work in the Snowflake seems to follow a logarithmic scale, the tenth step, the draft obviously being many times larger than the other steps together if you did things right.
I just recently, after having worked on my Snowflake for some time, came back and did changes to both the one sentence and one paragraph summaries—I had to because things had changed so much they were incorrect.
Don't forget that the Snowflake is just supposed to be a scaffolding for your story. In Randy's own words:
About midway through a first draft, I usually take a breather and fix all the broken parts of my design documents. Yes, the design documents are not perfect. That’s okay. The design documents are not fixed in concrete, they are a living set of documents that grows as you develop your novel. If you are doing your job right, at the end of the first draft you will laugh at what an amateurish piece of junk your original design documents were. And you’ll be thrilled at how deep your story has become.
If you want to, you can go back and fix the one sentence summary and one paragraph summary even after the work is done (for elevator pitches and the like).