Never take wavelength as an automatic reason for better burning at similar powers. Shorter wavelengths are not more powerful. 200mw of blue burns just as well as 200mw of green assuming the target will absorb each wavelength evenly. In this case, I would guess that the smaller beam diameter, and better beam quality are the main factors to better burning. But who has a green diode laser? Seriously who? Are you sure its not your typical DPSS?
mhm... the beam is thinner then my DPSS lasers.. and yeah... its DPSS I just call them diodes