According to game theory, vested interests will strive to maintain the security of the network, whether it is a mining pool or a small miner, so the security of the two is equivalent.
Let's take this to the logical conclusion. Communism.
No mining rewards at all. Purely deflationary currency. Transaction fees go to nobody. Hodlers are incentivized to mine blocks of transactions because it increases the scarcity value of their own hodlings.
However, there's a tragedy of the commons because your hodlings go up in scarcity whether you mine or not. There's nothing new under the sun. Perhaps this can be solved by purging any account that doesn't contribute enough signed mining shares.