There are quite a lot of series and I got confused about what sets them apart. So far I have seen series E, L, P, W, T and X in addition to their newer line of "Yoga" laptops. Can someone who knows about ThinkPads well explain me what these models represent or for whom they are designed? More on forum.level1techs.com

If you need the GPU then consider a W series. You can get an ex-lease W520 or W530 quite cheaply off Ebay now, although they are still significantly more expensive than a T series machine. A quick spot of ebay-fu suggests that your budget of $400 is achievable for either model, although you may have to shop around a bit.

I have a couple of W520s with 1600x900 displays, which I find to be a sweet spot in the compromise between screen real-estate and readable text on the screen. Some folks like 1080p displays. You pays yer money and takes yer choice, although 1080p screens seem more common than 900p.

Be warned, however, that W series machines are quite heavy and the 170w power bricks make the package even heavier - the total weight is nearly 4kg. You would definitely notice the difference between (say) a W530 and a T430 if you had to lug it around all day. If you get a dock, you also need to make sure you get a 170w model. I made this mistake once and a cow-orker appreciated my gift of a dock for his machine.

Assuming you want a W series machine (and don't want to pay through the nose for more modern ones) then the decision between a W520 or W530 is really down to whether you want an old style or new style keyboard. For a first approximation, the performance of the machines isn't radically different. W530s will have slightly better battery life.

More on reddit.com

E - Budget L - Budget plus T - Business work horse P - T series but with quadro options X - Lighter T X1 - Flagship Yoga - Flexiboys Z - Garbage More on reddit.com

Basically, P (replaced the old W/A/G series) - Workstation class. Beefier CPUs, and often a discrete GPU. Tend to be heavier and run hot. So more of a desktop replacement for engineers/scientists/etc. T series - General purpose higher end business laptops. Various options in terms of CPU etc. X series - Ultraportable. Smaller screens than the T series and sometimes has low power CPU options, but can have fairly beefy ones too. Useful for people who have to work on trains/planes etc... X1 - The fanciest thinnest ultraportable. E/L series (replaced the old R / I series) - Basically cheaper laptops for businesses/students who can't afford a T series More on reddit.com