You should consider trade volum, lifespan and innovation. I would only recommand peercoin.
Yes, I have watched Peercoin for some time now. The one thing that makes me cautious is that I am leery of inflation and have been unable to pinpoint the current yearly inflation rate. I know, funny coming from a DOGE fan but I am not looking for another DOGE, rather complimentary crypto-currencies to diversify my portfolio. I understand that the goal is to achieve a 1% annual inflation rate through Proof of Stake (which I think is excellent) but am not sure what the current rate is and when the end result target of 1% will be reached. If you can help or point me in the right direction to determine this, I would be appreciative.