SLA resin factors

Can someone please explain what determines if a resin can print at 10 microns. Dose the laser wave length,exposure time and viscosity have something to do with it. Interestingly I had a test part printed by Formlabs on their new Formlabs 3 machine and the surface finish was not quite as smooth as I had hoped. They told me this was because they were not able to use the grey or rigid resin that is used on the Formlabs 2 machine but were working on a resin that matched them that could be used in the Formlabs 3 machine. I do not understand why they would produce a new machine that would under perform and not give as good a surface finish as the Formlabs 2 machine.