In the event of a PoW change to enable both chains to continue functioning at the same time, the winner will be decided by user support and the number of services using that chain.
Here is a short list on the Classic side, they have quite a bit more than this BTW.
- Coinbase
- OKCoin
- Bitstamp
- Blockchain.info (Peter Smith)
- Xapo
- Bitcoin.com
- Foldapp
- Bread Wallet
- Snapcard.io
- Cubits
- Vaultoro
- Coinify
- Bitso
- Bitnet
- BitOasis
- Lamassu
- BlockCypher
- BitQuick.co
- itBit
Here is the list core has.
- Blockstream (nonfunctional)
- Green address
The result should be clear
I'm no longer sure.
If Bitcoin Classic uses Core 0.11.2 you'll have the choice
1.) Core 0.11.2 + 2 MB
2.) Core 0.11.2 + Pruning + libsec256k1 + many more things
Also, in the event of a change of pow, it would be everything but unclear who wins:
1.) a coin with highly centralized mining by a few entities
2.) a coin which is minable by GPU and brings us back in the lucky home-mining-days of 2013
Every exchange and marketplace will be flooded with request by enthusiastic customers:
"Hey, I'd mined some core bitcoins, can I sell them on your marketplace?"
I remember back in late 2013 on bitcoin.de we had a lots of customers from bulgaria. I then talked with them and they said: "Here in bulgaria everybody and his mother is mining."
there is no doubt who will win, in the back of all the minds of those who think this is even viable, is the longing for the days when you could make 1000's of present on your mining investment and get money for nothing. (Gmax can't mine with a 30% profit margin (needs 300%) so therefor mining for individuals is dead)
The market has moved on, if you try match energy input to security there might not be enough energy in Germany let alone enough GPUs on earth to mine a decentralized coin to protect a market cap of 15,000,000 coins worth $5,000,000,000. with just 7,000,000 coin left to mine.
it will ensure there survival but not make it a credible threat.
The protection of a coin depends on the avalability of hashing-power. The cost of a 51-attack is the sum of the cost of the needed hardware. If a coin is asic-resistant and has more hashpower than, let's they, the 50 fastests supercomputer of the world together, than you can say it's secure.