Instead of thinking which is more expensive, either in monetary terms or execution, perhaps we should see which gives sufficient security such that attackers are not incentivised to attack either. If it is infeasible for both kinds of implementation, then it's great. There isn't a need to compare which is more secure, because they are fundamentally different.
@ranochigo
Once the PoW attacker has set up their mining rigs, he/she is a few keystrokes away from the 51% attack. The hard part is setting up the rigs.
Sure there's a bunch of electricity that needs to be expended. But the cost of rigs + electricity is less than 51% of capital under PoS.
The question then is why are attackers not incentivised to attack PoW? Some possible reasons:
1) Requires ongoing electricity to maintain.
2) Overall cost is too big
3) Even if attack is successful, the attacker stands to lose everything (including said cost in point 2) and underlying coins going to 0.
4) They can't be bothered setting up the mining rigs.
Well let's comment on each one:
1) and 2) Yes but overall cost is less than under PoS. I linked an article which proves this and you didn't seem to disagree with the said figures
3) This argument also applies to PoS
4) This is true but if someone was to attempt a task as big as trying to hack the biggest network of all time, surely setting up the mining rigs is not an impossible task.
Based on this, my conclusion was if you think PoW is infeasible to attack, then you should also think PoS is infeasible to attack. Unless you think the major deterrent is the setting up of mining rigs.
Thoughts?