One major difference between the two companies is how they derive and drive their revenue growth. Tesla makes all their revenue from consumers from both primary (sell cars directly to consumers) and secondary (Tesla is starting a second-hand market for Tesla) market. Tesla now utilizes a B2C model, and is diversifying to B2B model through the production of batteries.
On the other hand, SpaceX derived almost all of its revenue from the US government through grants and contracts. As an investor, you have to take the risk of the revenue stream into consideration. Almost all companies technically go public because they need cash to drive future revenue growth (less focused on the bottom line). SpaceX has and always will be a B2B model unless space travel is made more affordable.
Some medias are saying that SpaceX will go public soon in the next year or two, but I doubt it unless they can diversify their revenue stream to private companies.
Intersection notepad 