SBDs shield you from losses, but if you're holding them and the price of Steem skyrockets, you'll lose those gains as your SBDs convert to less and less Steem. SBD may have a decent interest rate, but they're completely defensive. The only reason I can see for SBD right now is for those trying to time the market and buy Steem at it's lowest, but I'm not much of a trader!
The growth in vested SP will be the only way to reap profits if the platform grows. Liquid Steem should really only be held briefly between transactions. It doesn't defend against price drops and gets the most negatively impacted by the growth of available Steem, as it doesn't earn rewards to counteract that inflation. I'm just slowly building my SP with no intentions of cashing out for several years, in hopes the platform value grows and will lead to a real financial impact on my business.