The i7 in the MBA is slightly superior to the MBP based on benchmarks.
I wouldn't base my decision on the processor alone though, the difference isn't that big. Here are some other differences that could help you:
- Is the MBA 11"? If so would you prefer the 13" on the MBP?
- Do you need an Ethernet port? The MBA requires a dongle for that.
- Will you carry it a lot? The MBA is smaller and lighter.
- The MBA seems to have a higher resolution than the MBP based on everymac.com. Maybe verify this one, I find it surprising.
How much would you be paying for those? As you know, they are already kind of old, don't invest too much because macOS support might not last long for them.