It depends on your tow vehicle. Eight foot trailer has at least 15% more frontal area, often more because the two sizes are purposefully built to different heights, to address the tow vehicle frontal area issues. For some tow vehicles, particularly minivans, compact pickups, SUVs the trailer frontal area is a factor in the towing limitations.
Once past the tow vehicle issue, there is the driving part of it. An 7-foot trailer is easier to keep in a nine foot lane than an 8-foot trailer (or an 8 1/2 foot motorhome, I have one of those and try to avoid the really narrow roads). If your tow vehicle is wide enough, a narrower trailer might also be easier to see past, without mirror extensions out to ten feet.
FWIW, shopping for a small trailer for 1-2 person use, I am inclined toward an egg trailer only 6' 8" wide, barely wider than the full-size van that will pull it. That way I know if I can squeeze the van through a space, the trailer will likely make it through also.