To start, you can ask a question like this in megathread, as linked below. Just for future reference.
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Second, I’ve heard that the RS3M 2020 is very good, but if you have a higher budget, you could get a “better” cube. So how much do you have to spend? Lastly, I would say that an upgrade to a magnetic cube is a for-sure yes. At almost any speed, a magnetic cube will make you at least a little bit faster.