Not quite.
I am good friends with several Dell technicians who repair hundreds of Dells on weekly basis. They say by far the Latitudes are the most durable of Dell's notebooks, seeing only one or two per month. The Inspirons are seen the most because they are the most popular, and also less reliable due to the parts.
The first thing I did when I bought my Inspiron was replace the system memory and hard drive with my own. Since doing this I've never had any parts fail in any of my Dells. But by all means, avoid the XPS systems. They are marketed as toys and are priced as such. You should look on the Dell Outlet, as there are some great deals on Latitude systems.
Yes; do look at the Dell Outlet for some great deals! Avoid the
new XPS systems, but you can get some great deals on
outlet XPS systems. I got an XPS M1210 with much better specs than a similarly equipped Latitude for the same price, and $1000 off an identically configured new XPS. It just depends on the particular ones that they have in their inventory.
As far as memory, I wouldn't go over 2gb of RAM at this time. The price just goes exponentially up past that point to 4gb (like adding around $750 to the price of the laptop), and your performance gain will not be as big. Definitely don't go under 1GB for low-end vista laptops, and 2gb seems to be the sweet spot for all Vista systems at this point in time.
I only really chose Dell because my school does on-site repair under warranty for Dells only. Other manufacturers have to be sent off to the factory or done locally somewhere else. Example from my medical school's IS department (USF) regarding repairs...
Non-Dell Computers – Students that choose to buy computers other than our recommended brand may make an appointment with the Student Support Specialist for diagnosis of hardware problems but will be responsible for contacting their vendor/manufacturer and arranging whatever warranty service is available for their chosen brand. Because the time required for non-on-site warranty repairs that require shipping to a central repair facility, loaners may not be checked out for the duration of such repairs but will be available on a first-come first-served basis for short-term checkout for special needs such as presentations or tests.
Dell Computers – Students that choose to buy Dell computers may either work with the Student Support Specialist or simply drop off their computer at our office for diagnosis, and if repairs are needed we can initiate the parts replacement process and have the machine repaired in our office by Dell's representatives if they have purchased the next day on-site warranty. Several loaner computers are available on a first-come first-served basis while Dell computers are being serviced on-site.
Since I figure our time in medical school will be golden, I went with the Dell brands because I don't want to have to be without my laptop. Your school might be an HP shop or a Gateway shop, so you'll benefit with going with their recommended line of computers. Just my $0.02