Performance depends on several factors. For example, many additional features (such as duplicate detection, sessions, transactions, etc.) will add overhead, which reduces throughput. In case you want to compare this yourself, try running this performance sample: https://github.com/Azure-Samples/service-bus-dotnet-messaging-performance
In addition, since basic / standard are common tenant models, the performance you get today may be different from the performance you get tomorrow. In addition, you may not see the linear scale, as some nodes may be busier than others.
For true predictability, premium is your best bet.
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