Agree with the above.
However, an RS232 port is fine. I can sell you a £25 adaptor for a USB-only laptop - this is what I use. The advantage is that the data can come out on a decent quality connector, rather than the crappy USB connector. But this is only a detail.
It would be interesting whether the USB option results in a faster download. I don't think it does. I think all that JPI do is resell a USB-serial adaptor, in a little box
The EDM is a very old design (1970s) and I seriously doubt they have implemented a USB Slave interface in there, using one of the two chips on the market. But they may have done.
The actual instruments are not really pricey - if one looks at the US list prices. What costs as much if not more money is the sensor installation. An EDM7xx takes a day or two to wire up and fit the probes, and a lot of installers can't do it very well anyway. The fuel flow transducer needs some pipes to be made up (correctly otherwise you get turbulence and massive errors) and the transducer alone is $600 from the USA.