Short response is that at this time I think having a floating SBD rate is better for the platform. As the hordes of new people join Steem, they're going to want to see progress. If Steem price is high and SBD is low, it's going to take a long time to level up. I'm not trying to use Steem as a marketplace though, so it helps me more to have the price of SBD high.
The high Steem price means that I was able to buy enough Steem to get away from the 15SP delegation I was given. Because they took the delegation away at a 1:1 ratio (rather than the 1:2 I proposed) every time I earned more SP, it felt like I wasn't going anywhere. Now, I feel like I'm getting ahead and because I'm making progress I want to get more involved. This wouldn't have been possible with a low SBD price.