The main differences between these displays are the native resolution. The WXGA has a native resolution of [1280 x 800], WXGA+ is [1440 x 900] and WSXGA+ is [1680 x 1050]. Higher resolutions allow for more screen real estate (more will be displayed on the screen at any one time), however of course this makes text/ images/ etc appear smaller. These higher resolutions are desirable if you do a lot of spreadsheet work, gaming, photo editing, etc.
Now, Truelife screens as opposed to non-truelife. This is just the finish on the panel. Non-truelife will have a matte finish, whereas truelife screens have a glossy mirror-like finish. This gloss finish can make colours appear more vibrant although it comes at the cost of reflections in the screen. In other respects there is no difference between the glossy and matte.
IMHO, the WSXGA+ is the way to go, and for $100 from an WXGA option is certainly worth it. But different people prefer different displays.. it is subjective. I suggest you make a trip down to your local store which has laptops on display and compare a model there that has an XGA vs one that has an SXGA+ display and see which you prefer.