The first question I ask is:
1) What would be the most likely cause of Bitcoin's death?
The next question I ask is:
2) Which coin(s) (note I say coins not tokens) have a solution to (1) above?
I have been looking at question 1 above since 2011, when I first got involved with BItcoin, and I have come to the conclusion that the fixed 1 MB blocksize limit, and Bitcoin's inability to scale on the main chain is in fact the answer to question 1. Attacks on fungibility come in my opinion second. Furthermore second tier solutions such as the lighting network require scaling of the main chain in order to function, so while they do have very valid uses there are not a solution to the inability of the main chain to scale. At the heart of the problem lies the 21,000,000 XBT limit in Bitcoin, since this requires the eventual replacement of block rewards with fees to secure the proof of work. The trouble with this is: How does one make fees to rise? The answer becomes restricting the blocksize to create transaction scarcity. It is this that lies at the heart of Bitcoin's core opposition to increasing the blocksize. They are genuinely concerned about the long term security of Bitcoin and want to force the "fee market" while there is still enough block reward left to secure Bitcoin.
There is currently one coin among the top 10 in marketcap that has a solution to question 1 above, That is of course Monero. The reason is that Monero has both an adaptive blocksize limit and a minimum permanent emission of 0.6 XMR per block. The permanent emission ensures that Monero does not have to rely on a "fee market" in the future to secure the coin and fees can then be used to control the growth, via a market, of the blocksize by forcing the total amount of fees per block to compete with the emission. The net effect of this is that the total amount of fees per block becomes proportional to the emission so it becomes clear that fees can never replace the emission over the long term.
If one takes a look at other tokens one must first eliminate those tokens whose primary purpose in not their use as money. This does not mean that those tokens do not have value in their own right and may be worthy of investment and / or speculation. Examples of this are Ethereum, Ripple, NEM, Ethereum Classic and Stratis. This leaves Litecoin, Dash, Monero and Bytecoin as tokens that aim to be coins. Litecoin and Dash have fundamentally the same issue as Bitcoin. A fixed maximum number of coins and a fixed blolcksize. In reality all they offer is a "kick the can down the road" solution. Bytecoin is more interesting. It has the same adaptive blocksize limit as Monero but a finite number of coins. This is aggravated by a very fast emission curve and a pre - mine / ninja mine of over 80% of the max number of coins. The net result of this is a block reward that is already below Monero's permanent block reward and falling fast. I believe that it is simply a matter of time before Bytecoin is taken down by a 51% attack. It could also fall to one of the many attacks that Shelby Moore III has described under one of his many usernames in this forum. I know many in the Monero community see Bytecoin as the scam in the pre / ninja mine. I rather see Bytecoin as the canary in the coal mine, when one considers solutions such Bitcoin Unlimited. This air is getting more foul every 2 minutes and it is only a matter of time before the canary dies.
So what is left is Monero which also has the solution of a robust answer to the fungibility attacks on Bitcoin.
Edit: The Monero minimum emission is below 1% year inflation. This places it below the long term inflation rate of gold. For comparison it corresponds approximately to Bitcoin having a minimum emission of 3 XBT per block.
Is it conceivable that there could be a high enough volume of small-fee transactions that restricting the block size to raise fees would be unnecessary?
