First, check out your eyes. What size screen do you need?

Second, check out your fingers. What keyboards can you live with.

Third, check out your arms. What weight can you live with?

Then, consider the cheapest laptop that fits those three limits. Carry something that form factor around as you plan to carry your laptop, and at the same weight.

For most purposes, anything currently being sold has enough power. More ram is generally better than more processor power if you need processing power, and ram is pretty cheap, with a functional limit at about 2 gigabytes of ram.

Anyeay, look at it that way, then make your choice. By the standards of only three years ago there are a lot of incredible choices available out there.

Even more if price is no object.

Overall opinion? Windows suffers bigtime from the direct comparison.

I have a 12” PowerBook G4 and have been very happy with it, although it might now be time for me to consider selling it. iBooks are OK but not nearly so nice to work on, and PowerBook keyboards are far superior. And another good thing about PowerBooks is that they work seamlessly with external displays, keyboards and rodents.

Unless you cannot do without the power of a powerful desktop computer, with faster RAM, bus, hard disk, graphics processor, expansion bays, etc, why not consider having a PowerBook as your sole computer, and when working at the desk hook it up to a large DVI display? With a Bluetooth keyboard and mouse, you could even run it with the lid shut so that the graphics processor has to drive only the external display. With the lid open you have access to both (independent) screens.

Unless you have absolute need of the latest and best model, you would do well to consider a second-hand PowerBook G4 in top condition. As Apple fanboys tend to be obsessed with owning the latest models, you will often find as-new condition PowerBooks listed on eBay, but be warned that the resale prices of Apple computers tend to be significantly higher as a proportion of the new cost than for Wintel machines.

Some people complain about the cost of Apple computers, but looking at the various high-end Wintel machines available today, I’m not so sure this criticism is valid. Also, unless you zero-rate your time, you should consider also time spent farting about trying to get things to work properly. Macs are then without a doubt good economy.

The Mac laptops didn’t change design during the Moto/Intel switchover because they’ve gotten the design right; none of the inelegant Thinkpad buttons or that odd clitoral pointing device, and none of the garish clunkiness of Dell’s machines.

Toughbooks are freakish and magnificent but as an academic you’re not likely to benefit fully from them. A couple of engineer schoolmates of mine swear by them, though I can’t imagine typing on anything but an almost-full-sized keyboard.

Next criteria is horsepower. For what you want to do, a 5-year-old used laptop will do just fine. So again, it just depends on your budget. And yes, max out RAM if you can: even simple things like web-browsing can eat RAM like crazy.

Finally, ergonomics. For you, it sounds like ergonomics should be the only real concern. That means, keyboard, screen, and weight/package. This is where there’s no substitute for just trying these out in a shop somewhere, and deciding which “feels” best.

Apart from that, for your purposes the tech-specs are really negligible, execpt for the fact XP shouldn’t really be run with less than 512 RAM and you might consider having 1 Gig for Vista.

Do you at least know which operating system you want? The new Fedora is awfully slick, and next month’s Ubuntu update is supposed to be the bee’s knees, but linux is always peskier than either XP or OS X. XP has widest range of software, if you go for that sort of thing. Someone mentioned indulgence above: custom paint job…

I heartily second maxing out RAM no matter what you get, then getting the best combination of cpu, hard drive, and other hardware.

Oh, and a friend who owns Dell tells me that, if you do choose Dell, the three year warranty is a wise investment.

Either way – pay attention to the case. Go look at some cheapos in the big box stores. See how flimsy the flip up screens are. Run away.