Short of affecting a coin whose market cap could somehow dynamically adjust to all economic variables to maintain stability and use, the broad Devcoin model is the next best thing. Even if it was possible to maintain that first dynamic option on a local scale (by adjusting for factors such as money supply, circulation, velocity, birth/death etc), that’s pretty much impossible globally. Already the purchasing power parity aspect is very diverse with for example a Bitcoin, price moves and spendability meaning quite different things to say an American than to an Indian (i.e. there's no consideration in the model for locality and economic variables - there are pros and cons of this).
The reason this matters most is not really or only due to the competition or developments among various cryptos to date. It’s because e-money is coming to where you live regardless - central banking, private banking, governments, and people. There are going to be a lot of 'alts' so consideration needs to be made of the competing end(ish) games underlying the big experiment.
So ubiquity should be the goal. Price today is not the same as long-term value. It's quite possible for varying models to serve particular interests and markets but that won't necessarily translate to real mass adoption. Devcoin has the infrastructure and technicalities to progress to the general public. It’s the rate of growth - trending lower over time - that matters, not the headline per period money supply - as that % of total obviously falls over time.
And on the issue of negative interest I think that's going to happen anyway so the possibility, and the consequent effects on competing alternatives should be considered, particularly in the context of currency, circulation and today's deposit banking model which is dying (been highlighting it for a while on devtome negative interest rate policy). I appreciate it might sound mental today but it's notable in the context of e-money and I’m not making a point on whether that’s good or bad, just a policy forecast.
The other issue is the debate over relative security and control. Particularly what the long-term effects might be for decentralised block chain currencies when an underlying incentive exists to control as much computational power devoted to mining as possible so long as my profit >0 (a dynamic perhaps more obvious with some alts). Devcoin is already merge-mined with Bitcoin, so any security concern is minimised versus others and there doesn’t need to be any conflict - both concepts working to achieve mutual benefit for the others and varying users.
tl;dr
Frankly I think it all comes down to long-term stability, distribution and compensation. It’s a model like Devcoin that can achieve stability in the future, get currency out to the widest subset of the population, and as the projects/models are developed and decentralisation grows tie that all in with compensation for work in a cryptocurency beyond just miners - something (again like it or not) that could have mass appeal.
+1 I think our discussion needs to be right on the front of "What is devcoin?" this will definetily put the seemingly awkward technicalities in perspective of real world applications and thus adoption for the future. Great post and if everyone coming to rhe project read our discussion the visiter to adopter rate would be massive!