The "Best Scanner" is very subjective. What are your needs? Accuracy/Speed/Cost/Ease of use, etc.. are all factors.
If it's accuracy, then it would be the 3shape 2000 at ~5 microns vs. the Medit Identica Hybrid at ~7 microns vs. maestro 3d MDS4000 at ~10 microns
If we're comparing speed:
Medit Identica: ~16 seconds for full arch scan
3shape D2000: ~20 seconds for full arch scan
Maestro 3D MDS400: "2/3 minutes for scanning and digitizing a work session"
Footprint:
Medit: 290 x 290 x 342mm
Maestro: 400 mm [W] * 300 mm [D] * 265 mm [H]
3Shape: 480mm x 320mm x 280mm
Price:
Medit: ~$15,000
Maestro: ~$20,000
3Shape: ~$50,000
Without more details... can't really say what the best scanner is for you