Let me attempt an answer using only canon (TV and movies) content.
Answer: Unclear, but holodecks are extremely high resolution. If LaForge can tell holograms from reality, it's because of the range frequencies of the radiation, not the holodeck resolution.
In "I, Borg", we have this exchange regarding Hugh:
CRUSHER: That's right. He's gotten every one. Eight out of eight. That blows the top right off the spatial-acuity percentiles.
LAFORGE: It's the prosthetic eye. It seems to be giving him very complex visual information.
CRUSHER: Like some kind of holographic imaging system.
LAFORGE: That could be helpful. Hugh, I'd like to take a closer look at your eyepiece. Is that okay?
In other words, Borg ocular prosthetics are technologically remarkable, even to LaForge, who knows a lot about ocular prosthetics (and a lot about a lot).
Yet, in Star Trek: First Contact, it is shown that Borg can be fooled by the holodeck when Picard and Lilly hide in the "Dixon Hill" simulation.
Hence, we can conclude that if LaForge can distinguish a holodeck simulation from reality, it must be due to differing abilities of his vs. Borg prosthetics. And given LaForge's comments, it appears it can't be due to basic perceptual ability like resolving capability, since that is apparently better or equal for Borg compared to himself.