Ensure is extremely sweet. Living off Ensure, you'd either have to get the zero carb version, or you'll have 2x the sugars of Soylent. It's also just disgusting to drink more than 3 of something so sugary before needing something else. The original Soylent flavor I can have for weeks before feeling like I need a change.

If a cheaper competitor emerges that doesn't taste like a milk shake, I'd switch to that. But so far no one has offered a reasonable alternative.