So 330/275 = 20% better.
Yep. The actual physically relevant number is exhaust velocity, which is the mean velocity of the particles in the rocket exhaust.
Isp = Specific Impulse = exhaust velocity/(9.81ms^-2).
9.81ms^-2 there is not any actual acceleration, just an agreed conversion factor.
The unit of Isp has no physical significance, the convention just arose because early rocketry was a collaboration of people who all used different units, and they wanted to be able to compare numbers. Since the unit they all shared was a second, and they all agreed (roughly) on the real value of g, they just divided exhaust velocity by their g to get a number that could be compared. The convention stuck.
I'd look it up but my textbooks are in boxes, but the units everyone uses are wrong. Actually inappropriately simplified.
 I have one and exactly one textbook that has the full units for gc.
due to the exponential nature of the rocket equation, 100 tons of fuel will result in 2 tons to LEO in the former case and just 1 ton in the later.