I would have to say (in my own opinion though) that the John Lowe barrel original or current, would have to be the best Unicorn Dart.
The reasons I say that is I beleive due to the 35mm barrel (21g) there is nowhere else to grip except where was intended=the middle. center weight & in JL's words.
"Its a simple barrel yet effective"
Have used the dart many times over, it certainly shows you if you make a mistake the barrel is NOT going to change its path much at all, simple dart and it makes for easier play and less stress mentally.
Having said that we all here have our own choice of dart naturally and do well with them but that to me is the best Unicorn barrel.