For me, having its value on a spike or the quality of being highly volatile is still the better option for me, having this quality means I would be able to play may money and earn profit on my own. Having a steady growth is fine as well, and I can see many investors being happy with it, but I would choose the highly volatile bitcoin.
People must understand the fact that bitcoin is volatile, and it happens to be powerful source just because of this one feature. Remove this one nature of bitcoin and see the clumsy results.
Bitcoin can function just as well, if not better without the high volatility, it would remove a lot of people who are only here to speculate on wild price swings, most of those people couldn't care less about bitcoin's future and are only concerned with short term wealth.
Those people are not going to leave the market even if the volatility was very low, because in what other market they can invest money without revealing their identities and where there are almost no rules and make money that way? Most other markets are very regulated and many of the things that people do in this market are illegal in those markets so they are not going to leave even with the lesser volatility.