The downside is that you're not investing into steemit, you're investing into steem. Steem being something that could in theory become worthless while steemit maintaining its value. That scenario is highly unlikely, but it is still an important consideration. However, with steem your time is actually a more worthwhile investment than your money. Since by putting your time into it, you provide volume to the currency, not in the form of trading but in the form of attention. Attention then will transform into something, or won't. Personally I hope it will transform steemit into something that isn't quite so unpredictable. There is some form of culture, but is hard to grasp.
I think you mean that steem can maintain its value while Steemit may collapse but yes. The time that goes into Steemit is worthwhile for building the platform but, it is the mining aspect that creates the value. Lots of exciting (potentially nerve wracking) times ahead :)
Actually what I mean is that either way can happen. Like I said, it is very unlikely that steemit would maintain its value when steem collapses (steemit is a business). Also steem could survive the fall of steemit.