Well, to be honest for the best external appearance in my opinion and many others on this forum the wider 285's are the best bet. Once they are mounted they just look like the VX was meant for a 285 tire, and the cutting is to the underside of the plastic, it is very minimal and only on the front. If they had not already been on the VX when I got it I probably would not have taken the chance either, but man I am glad they were already on there. But it is your call, and the 255/55's would definitely fit on the rim here is the info from Nitto on the 255/55's:

Tire Size = *255/55R18 109S
Stock # = 200-440
Tread Depth = 10.1
Inflated overall diameter in inches = 29.02
Overall width in inches = 10.43
Approved rim width in inches = 7.0-(8.0)-9.0
Max load pressure = 2271@50
Revs per mile = 717
* - Indicates Extra Load (XL)