So I should probably buy the US software online to get the best results? Or it might not matter?
I'd say, if you can get the NEC software (SpectraView II), get that!
There are several EyeOne products. EyeOne Pro IS a Spectrophotometer. EyeOne Display is a Colorimeter. IF you can build printer profiles, you have a Spectrophotometer.
A colorimeter is a better device for display calibration and profiling due to its ability to handle very dark emissive measurements. The problem is, they have filter sets that are (ideally) mated for a display type or at the very least, a general assumption of the display. Most are expecting sRGB. So, with a wide gamut display, you'll get improved white point measurements with a Spectrophotometer, you'll get less than ideal dark measurements. The NEC software allows (via a clever trick) to use both. Note that Karl Lang's testing for PPE, using a Colorimeter with filters expecting sRGB, on a wide gamut (2690), the actual measurements were off about 500K which isn't unacceptable but, its off.
If you look at the really nice NEC very wide gamut LED device, NEC did the best thing, they OEM'ed a colorimeter from X-Rite with special filters for their device.