Glossy or matte has nothing to do with it. It's all about consistency and bitdepth.
Laptops are crap. They are TN film panel screens since they are the only ones that can be made light and thin and cheap. They suffer from horrid viewing angles (giving you no consistency, repeatability, or accuracy), and produce only 6bit colour. Calibrating them is like polishing crap. It can be done, mythbusters did it, but ultimately you end up with a shiny ball of crap anyway.
Given the choice get an external screen, but don't get the cheapest one you can find or you'll end up with a TN film panel again. At the very least you want a PVA panel which has much better viewing angles and can actually display 8bit colour. But ultimately what you really want is a IPS screen since they produce perfectly consistent colour across viewing angles, and depending on your budget you can get an IPS screen with an internal 12bit lookup table where rather than fudging the output to make your screen appear calibrated, the screen stores a table of values based on a correction curve.
Grab the model number of whatever you're thinking of getting and type it in here:
www.flatpanelshd.com - Your guide to flat panel monitors and TVs - Panel Search to tell you what kind of panel it is.
Also note that there are quite a few screens on the market which advertise wide colour gamuts (the standard is advertised at around 70-75% of the NTSC gamut, but screens with 90% and even bigger can be found for cheap). This will thrust you into a world of colour management hell. Quite manageable but expect a learning curve.
Summary: PVA or IPS panel, not TN.
All other details are far less important for calibration.