I would say that mining is much riskier than holding bitcoins because bitcoins are designed to grow in value whereas mining hardware and reward is designed to decline in value due to competition. It is that profitable only before the hashing market saturation (and GPU mining seems to be unprofitable already). Also mining requires to deal with noise, heat, electricity bills, hardware failures, etc.
I contend that an ideal crypto-currency should allow everyone who owns it to profit from its use and that owning & mining should be equally profitable. This would be accomplished by paying dividends to owners from 50% of the transaction fees.
When you hold a bitcoin, you benefit from the growth of Bitcoin economy via deflation.
When you send a transaction with low fee, it is the same as if you were sending it with a high fee and receiving part of its cost as dividend.
So according to your definition, Bitcoin is an ideal crypto-currency.