any disadvantage to a lighter ski

Maybe a dumb question but is there any disadvantage to a lighter ski, say 22 #, 10kg, vs. 27 #,112.27kg?

Depends on where your going to paddle it, your ability and your weight.

The only thing that's for sure, will be it's easeier to get on and off the car.

Yes, a lighter ski is a lot more affected by wind and waves which makes it more unstable especially in rougher conditions.