Let's consider Proof Of Waste for a second. 51% of Bitcoin's hash power is on 2 to 3 mining pools. The paid NOTHING to obtain it. You are entrusting them directly (or indirectly when they get "hacked") to not fork your coin. By the way... this statement I can back up with facts and readily available data.

First, it's not "waste". It's a highly specific impossible to forge or reuse effort to ensure security while also fairly converting value (energy) into tokens, bridging the outside and indise economy seamlessly.
The pools and their costs argument is only temporarily valid. The pools paid nothing, but they have nothing long-term. If they fuck up, miners will move quickly, miners paid A LOT of money for their power and have not usually recouped. I am entrusting the miners that need to collaborate and play fairly to profit.
You see the difference now?
It is waste in that it wastes electricity and processing power unnecessarily as has been proven by PoS. This is something Bytemaster (Bitshares main dev) came up with, for the Bitshares community to refer to PoW as Proof Of Waste to point out the fact that it is unnecessary to expend these resources simply to secure a block chain, as is proven by PoS and all of its variants.
I will concede you have a point as to the pools only being able to mount an attack temporarily before everyone switches pools. However, I stick to the fact that you simply made up "as it happens for many coins an exchange owns more than 51% of the supply", and you have no proof of this and it is not true. The point was that there are different attack vectors for PoW that exist other than achieving 51% of the hash power. Both PoW and PoS variants have vulnerabilities and different pros and cons. There is no perfect solution, and I believe that PoW is often touted on these forums as being a perfect solution when in actuality it is not.
I disagree again.
It is not waste, it is a conversion of energy value into coin value. PoS coins (various types as you mentioned) also use a method to get value into the coin itself:
- PoW stage: it's the same as a fully PoW coin, just that coin emission ends very quickly and is unfairly distributed with regards to future investors.
- gib muny: just "devs" ripping off investors and collecting pots of bitcoin (the irony) to give price decaying coins to them
There can be only one instance of proof when an exchange owns 51% of the supply, when all depositors account for all deposits in various known addresses and reach a 51% sum, otherwise it's not ensured that you can detect a 51% ownership.
Again,
PoW attack vectors are valid for mere HOURS, while a PoS attack vector can be used FOREVER once it opens up. This is a very HUGE difference in the security model which reduces the effect of the attack.
This is not accurate. All decentralized consensus algos are vulnerable to 51% attacks whether it be PoS or PoW. Someone with enough hash power to 51% a PoW network can do so forever, or until the PoW network forks and changes PoW algos. Someone with 51% stake of a PoS coin can 51% the coin forever, or until the PoS network forks and burns the attacker's stake.
Going back to the PoW "waste" which you pretty headed PoS supporters don't seem to understand not even 6 years after Bitcoin was invented. This is not "waste", it is a cost that is converted into new coins (scheduled or fees) from block rewards. The approximate cost to generate a block is found in the value of new tokens. This cost is real and significant, this gives value to Bitcoin.
The cost of generating PoS blocks is basically zero (5$ a month for electricity on donated hardware or a VPS bill). The value of the block rewards is thus zero, this gives no value to new PoS coins, the market cap remains the same, but new coins are added. Price per existing coin will be lower.
What does this mean? Let me show you:
PoW
Bitcoin: 0.7% price growth every day for 6 years, 5,678,828,589 USD market cap
Litecoin: oscilating but stable parity with Bitcoin for 3 years, 138,439,389 USD market cap
Namecoin: oscilating but stable parity with Bitcoin for 3 years, 10,064,647 USD market cap
Hybrid
Peercoin: oscilating but stable parity with Bitcoin for 2 years, 18,474,609 USD market cap
Novacoin: down the shitter in 2 years, 640,582 USD market cap
YACoin: down the shitter in 2 years, 37,320 USD market cap
PoS
I'll let you pick the best examples older than one year
It is waste though in that it wastes electricity and processing power unnecessarily to achieve decentralized consensus. As to your price examples... purely PoS coins havent even been out a full year so it is too early to make those comparisons, but I speculate that it will be no different than PoW coins. Bitshares for instance has increased in value this year, whereas Bitcoin has gone down in value. You can cherry pick data points that support your argument, but it doesn't necessarily mean what you are saying is true.