I invested in curecoin and then found out about gridcoin. Both are "help the medical world" coins. Which one has better LONG term prospects and why? Are there other coins in this sphere?
GridCoin has a large community with a diverse mix of projects, but it has some exploits in its history, and overall output of the BOINC network in terms of PetaFLOPs is about half that of Folding@Home. BOINC projects are hard to value. People are crunching 10x more RAC on MilkyWay than Rosetta@Home. It becomes a question of priorities. But certainly they have a larger platform to experiment on, like their Neural Network statistics server and the finance project they experimented with. Perhaps what makes GridCoin somewhat confusing to me (and I mine and hold it) is the eccentric relationship with bitcoin utopia whose RAC on the Gridcoin network exceeds the TOTAL out of the network by a factor of 40!
I think you have a slight missunderstanding how Gridcoin rewards work, Bitcoin Utopia does not pay out more Gridcoins than any other project. Each project pays out exactly the same amount of coins, independent of how easy it is to get RAC in each project. How many coins you get depends on (your RAC/sum of all RAC in this projet in team gridcoin).
So Bitcoin Utopia does not "produce" any more coins than any other project.
As you can already imagine, I have a very strong preference towards Gridcoin, as it is the only decentralized coin out of the three, which is a must for any cryptocurrency.
This was technically very hard to pull off, but it works and now with the recent addition of the pool (pool.gridcoin.co) it has also become easy for newcomers to mine/research. Gridcoin also works for many projects and not only a single project.
Another big advantage is the possibility for custom projects, which does not exist for the other coins. It is possible to create commercial projects, for example for stock trading, machine learning, data mining,... that uses the computational power of the Gridcoin network for free (it's a whitelisted BOINC project basically) and for this has to so something in order to stay whitelisted, for example buy coins on the markets and send them to a burn address.
This would truly raise the value of Gridcoin and also makes sense for the commercial application, as the computing power is still much cheaper than commercial servers. This is where I see the true potential of Gridcoin. But a fixed amount (say 80%+ of all computing power in team Gridcoin should always go to science for free).
edit: The reason why I think these "science coins" will become much more valuable is that it is very easy to convince people not in crypto before how good of an idea they are, see for example here:
https://www.reddit.com/r/Futurology/comments/4b4drk/a_currency_minted_by_doing_science/