Most likely, there are even variables you haven't thought about yet! How can you make a decision like that easier?
Just ask "future you."
Let's use the decision of your builder as an example. Two years from now, what would have to happen in order for you to look back and know that you chose the right builder? Make a list of everything that needs to happen from start to finish for you to be able to know that in the future.
You may want to consider questions like these when you make your list.
Would you want to look back on a builder that walked you through the whole process, or one that passed you off to a lender to come back once you've been qualified for a loan?
Two years after your build, would you remember your builder providing an interior decorator to work with you to choose your finishes? Or would you remember running all over town trying to figure out if your carpet and tile would work together?
Would the builder work hard to help you stay in budget, or leave it up to you to figure out when you've gone over budget?
Think about how you want to look back on your building process. Would you make all your decisions up-front with expert guidance, or would you want to make selections on the fly as construction progressed? Which one would stress you out, and which would make you feel confident and relaxed?
Do you expect your builder to be available to answer questions and help with any needed repairs, or do you want to be done with your builder after your home is built, and handle those things on your own?
Visualize what experience would make you feel confident you chose the right builder. What would make you happy you chose a particular builder, and what would make you regret choosing a particular builder?
Use that visualization to create a list of the criteria you require form your builder. You can use that list to develop questions to draw the information you need to know from each builder you're considering.
Don't fall into the trap of only comparing price and "standard features." A lot of your home-building experience will depend on the builder you choose, so make sure you choose a builder whose strengths match the list of your criteria. That way, "current you" can make choices you know "future you" will be happy with.