As it was explained to me by objet, the X/Y resolution is the size of the individual droplets of resin that can be laid down by the Connex's digital print heads. They are larger than the thickness of each layer, therefore the resolution is better in the Z-axis than in the X & Y.
In Formlabs case, I would imagine this is the 'width' or diameter of their laser. The way I read it, the smallest cured point they can produce in a layer is 300 microns, or 0.3mm.
The Formlabs printer does look well polished, but I don't think it is 'disrupting 3D printing'. the B9 Creator* is in the same price range with higher resolution, and may have the ability to include multi-material printing eventually. I believe resin may be cheaper for the B9, too.
[EDIT] include link to B9
When we talk about minimum feature size, we are giving a rough guide for the finest pillars or walls that you can print (see the fingers of the Neptune figurine in our photos). By this metric, the Form 1 is comparable to the best high end SLA and inkjet machines, and well beyond any FDM machine.