You're right. Lower rakers helps, but it doesn't have that hard corner working for it like full chisel. Pretty well established that full chisel is faster chain.
To be clear, just because a chain is semi-chisel doesn't make it safety chain. Far from it. On the other hand, there's also plenty of safety chain out there that's full chisel.
When I want to keep cutting in dirty wood, I use semi-chisel. If I'm cutting cleaner wood I use full chisel. My preference based on experience.
Last but not least, even safety chain can cut well when sharpened properly and the rakers are adjusted correctly.