Work is Windows-based so I run a VM on a MacBook using VMWare Fusion so I could use Windows-specific software
For work, I have to analyze very large datasets.
I want to have 16 GB of RAM to future-proof the laptop
Per the above statements you want to choose a MBP with 16GB RAM, potentially 32 depending on the size of the datasets and the software you're using to work with them, but probably fine with 16 since if you do have to swap virtual memory, the SSDs are pretty quick.
The MBA is great for brief bursty CPU usage with periods of idle time. That is not your workload. You need a system that's intended to support sustained substantial CPU loading. That's a MBP.
Given your ~4 year ownership cycle, I'd suggest going to the 10th gen MBP systems as well.
As an aside: I consider the concept of "future proofing" as bullsht. Your expected needs are your expected needs, and if you allow a little headroom for growth through your expected ownership cycle then the system fitting those needs will be great. If your needs change sufficiently that you'd wished you'd "future proofed" you probably would be better off replacing the system for other reasons as well.
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