A lot will depend on what resolution the LightJet is run at. The paper based units can run at 200, 305 and 406 ppi (don't go with the lower resolution, IMO). The enlarged negative will have more detail than the same negative scanned and printed on a LightJet. However the LightJet print may look sharper, since you can apply sharpening to the digital file. I like unsharped prints with more detail, as I think they look more natural. As far as tonality, I think they are both about the same, assuming a good scan.
I have a film based LightJet which runs at 2016ppi, and the sharpness and detail you can get on paper (up to 11x14) are amazing. So if ultimate sharpness and detail are need I think this option is the best I have seen. Of course it's not running now, and my enlarger is.
You should also compare the Chromira. It uses leds instead of lasers, but I think for normal prints it is a bit sharper. Both are continuous tone units.
Having said all that, I am gradually finding I like my color work output on my inkjet better. And this is simply because of the choice in papers. All the RA4 based options (LightJet, Chromira, enlarger) print on RC papers. With inkjet there are now some really nice papers that look and feel like the B&W fiber based prints I make in the darkroom, which are my favorite.
All of what I have said is for color work only. For black and white, stick with the enlarger and FB paper, IMO.