Thank you all for your replies!
There seems to be a distinct lack of consensus out there on the best way to go, with perhaps a slight bias in favor of the 2011 processor. So it looks like we'd do okay regardless of whether we get the new machine (as is, without upgrades) or go with a mid-2010 with either RAM or SSD upgrade. Which means, at this point, that it'll depend on price . . . and we'll just have to grab the best deal we can. My personal bias would be towards new, but it sounds like he'll do fine either way.
This raises all sorts of other questions about backup HD's (can you really put the backup drive in the laptop???), but I guess the only thing I really need to know is if there's anything (other than keypad protector) that we should get now. If there is, I can be looking for it at the same time.
Many thanks again!
The backup can't (and shouldn't) be installed in the computer, but it is a very good idea to have one.