My philosophy has been this:
What are the best technologies from a technical and privacy side
What is size of the market opportunity they address
Firstly, I hear from engineers who are students here in my town what the best coins are. I only buy the ones that the engineers say are well made. Then, I also compare it to the potential market size of the opportunity if it’s successful.
I’ll give you an example: a lot of people felt that Ethereum has better long-term prospects than Bitcoin. But I disagreed with that because I looked up market sizes: the market for payments (Bitcoin’s purpose) is bigger than the total market size of all software (Ethereum’s purpose).
Now, that being said, I could still be wrong because Ethereum can be used for both payments and apps, but it would require some major technological improvement for them to do both and not clog the network, as is already happening. Ethereum already slows to a crawl when new ICOs (apps) come out, and basically none of the Ethereum apps even have users yet (or not a substantial number).
The other coin I am interested in is I/O Coin (IOC) bc it is an attempt to make a new Domain Name Seever, the backbone of the Internet, out of the blockchain. With governments like China censoring the internet and especially blocking Bitcoin, this could be a huge opportunity.