In a few different cases (one node, one browser-based) I've had medium-sized read-only datasets of a couple million objects where I've tried to conserve memory by using typed arrays. While it saved a good amount of memory, property access was significantly faster via objects than typed views. I'm curious to re-run the benchmarks with Turbofan though, maybe things have changed.
Indeed, it heavily depends on what your JS engine thinks your data types are, your allocation patterns, and more. If your engine thinks you're using floats to index into a typed array that might be slower than using floats to index into an object. Even if you know your numbers are really only integers. Which is why JS performance is so puzzling sometimes.
One thing you can do with typed arrays that you cannot do with objects, though, is zero-copy into workers. You can use that technique to get pretty much free parallel performance on any number-crunchy task.
These things change all the time though; all the more reason for always measuring before you cut and investing into better profiling tools.
