If you would choose a blockchain from scratch ... which would it be?

Thought experiment: all of last year's bitcoin history just happened in a parallel universe, and you all have no access to the main blockchain.
You do have the source code, and are free to start/join any blockchain you'd like.

Which block chain would you invest in? (What characteristics would you tweak from the current main blockhain?)
In fact, I guess you should keep a portfolio of coins from several different blockchains. How would you allocate that portfolio?

The main tweakable characteristic of the current chain is it's maturation time: Let's call 21,000,000 bitcoin 1 Megatoshi.
Then, the key difference between the chains is the "Megatoshi half life": the current chain has a half life of about four years - every four years the number of bitcoins not yet generated is halved. How would you diverge your portfolio in this respect? Would there be sense in investing in different blockchains with the same half life and other characteristics, or will there be only a few different chains, and no two chains will have the same intrinsic characteristics?

Note that this has a real impact on the potential growth of your chain - too short a half life (like 10 minutes) means that all the coins are generated too fast, the public doesn't have enough time to join, and your coins will essentially be worthless. A half life of a millenia means nobody can generated hardly any coin, and your coins are again worthless.

Four years seems like a magic number (another credit to Satoshi's brilliance), but I'm wondering if in this thought experiment you would want to diversify at all. Perhaps even in this case the masses will converge into a single block chain, simply for the added security in masses that the dominant blockchain conveys.