Socialize medicine. That's as far as I go. 😉
I prefer the option of: whatever is actually best for the topic in consideration. I do not believe that one-size-fits-all works in all situations. Socialism, to me, works for items that are necessary but (a) from which private companies cannot sufficiently profit, or (b) private companies would be far too much disruption.
National security, border, police, highways/roads, military, many utilities, etc. All of those would be impossible or impractical for total capitalism. It is really hard to have a good military run as for-profit. I guess that is just replicating the mafia. Did you pay your security fee this week or do we let Canada invade your neighborhood?
Just imagine the criss-crossing road network if 5 different companies had to each separately connect you to your job, stores, and entertainment. Plus the expense of tolls and time in line going through barriers on each road keeping you off of the other roads for companies you don't subscribe to. Or imagine the expense if you had to run 10 different sewer lines to your house to be able to have capitalism work in competing water treatment plants.
For almost everything else, capitalism usually works well. It has the one key thing that socialism struggles with: personal loss if you don't keep focused on the necessary tasks and work hard at them. On the flip side, once you have nothing, personal wealth loss is no longer an incentive since you have nothing to lose. So, capitalism struggles with the bottom of the wealth ladder.
Intel is an interesting case: economies of scale are making virtually all companies but one drop out of the cutting edge race. So, capitalism in fabs is reaching the state of a situation where private companies cannot sufficiently profit. Whether it is a true national need is something that I'd leave for the P&N topic on it.