The green laser is a lot more complex to build; it uses a solid state pumping for generating green light - a highly inefficient process.
Blue lasers have been made common by the DLP projectors manufacturers; a projector have more than a single diode... Some time ago most had 24 diodes inside, each capable of ~1.5W (!!!)
The green hits almost the peak of eye sensibility, so a single mW of green can be as strong as five mW of blue.
So 300mW green, being more expensive (considering you're talking about a reputable company selling these) would be more bright and would have a smaller divergence (which is desirable).
The blue, with a big divergence in one axis, would rely on its power to maintain long-range visibility.
People have been spoiled by the power... both are bad ideas if you never had a laser before...