Wacom and N-Trig both offer projected capacitive based active pen/digitizer. N-Trig calls theirs Duo Sense 2 (SP3, SP4, Surface Book, VAIO Z Canvas), Wacom calls theirs Active Electro Static or Active ES (Thinkpad Yoga 14, Miix 700, HP Spectre X2 12 etc...).
They both work largely the same: Use capacitive touch screen for positional polling data at high speed (>120Hz) via powered pen, use a load cell pressure sensor tip assembly on the pen for pressure data, communicate with the computer via projected cap screen without any additional protocol such as BT.
The physical performance difference between the two is the pressure load sensor, but not in the amount of the pressure they can sense, since this can be artificially be jacked up to whatever number you want (currently Wacom allows ODMs to set theirs up to 2048 levels. N-Trig caps it at 1024 levels). The real difference is how much pressure does it take to initiate the sensor to engage (Initial Detection Force or IDF). Lower is better, Wacom is very low, and is proud to advertise this: 1 gram. N-trig knows their is not as good, so they do not advertise the number, so I can only guess, but I know it's higher than 3 grams. Probably around 5 or so.
Also important difference (for now), is the software support for the pressure. Wacom has been at this for very long time and just about every damn art software out there supports their Wintab driver. If you have an old legacy app or quirky less known app, you want to go with Wacom to ensure that pressure is properly supported. The only software that I know supports N-Trig better than Wacom is Microsoft's own Fresh Paint, but that's because the original devs quit and it now supports neither pens well at all. Anyways, until the new universal Realtime Stylus (MS) API is supported by all legacy software (still far from the case), Wacom will have this software edge over all other pen tech.