in a 1st world country, a mix of the two is neccessary otherwise it wont be a 1st world country...
in a purely capitalist country then people at the top would outsource the jobs to the cheapest labour market meaning there would be massive unemployment...literally over 50% as there would be no manufacturing whatsoever....the service industries would also collapse as there would be noone able to buy services...because of pure capitalism there would be no social security and so no benefits for those unemployed to fall back on
there would also be far less tax going to the government to provide any kind of service the people and so infrastructure would begin to fail
needless to say...after 10-20 years of pure capitalism the 1st world country would end up a 3rd world country
in a purely socialist state there is little incentive for big business to stay located there...they have the finances and resources to upsticks and move to a more capitalist friendly country...
so the best working model is a mix of the two...a capitalist friendly tax system to encourage big business as well as a decent social security system to allow support of people who fall on hard times
i think the US doesn't really have the right balance at the moment and it needs to change now while it is the sole economic superpower because once China and India gain more power then it's not unfeasible that large US businessess that would foot the extra cost for more socialist policies (a publicly funded healthcare system for all...better benefits for unemployed) would indeed upsticks and move to one of those countries.