Is it more dangerous when 51% attack happens than just having a pool with >50% hashrate? Many people told me that, if a mining pool performs a 51% attack, the price of the coin will drop.

But I disagree.

There are pools with >50% hash power already for a long time. Flypool is an example. (On the ZCASH network)

If one day these pools start to mine only on their own blocks, but not double spending or refusing any transactions, they performed a 51% attack. However, I think the security risks didn't become higher.

Yes, they can revert a transaction at any time so it is a security risk, but they already have had this ability for months!

For these two situations:


there is a pool with >50% hashrate
this pool mines only on their own blocks


I think the second is not more dangerous than the first one.

So my question is, is it becoming more dangerous when a pool with >50% hashrate starts to mine only on their own blocks? Will the coin price drop and why? Why didn't pools like Flypool mine only on their own blocks?
One can't say what's more or less dangerous for a cryptocurrency value. You don't have a control group. You would need a parallel universe where Flypool had no more than 51% to compare prices there to prices in our universe.

Saying that, being decentralized it's the very point of a cryptocurrency, and very few people will invest in one of them that's actually centralized. I can only speculate what's in their minds, but maybe people invest in ZCash today hoping it will become less centralized in the future. Flypool, despite having more than 50% hashpower, like you said, probably don't mine only on their own blocks because they would make people sure the thing it's centralized. Or maybe because they sincerely want the security of ZCash against a double-spend, so the accept the smaller pools help. Both things must probably increase an overall reputation of the ZCash in people's mind and must probably keep the price a little high.