You definitely don't need to worry about your laptop being fried by the higher-capacity power adapter, because the laptop will only draw what it needs.
My 6-year-old laptop came with a 65W power supply. When I bought it, I could have gotten it with a 90W power supply, but I opted for the smaller power supply. The docking station that I purchased later came with a 90W power supply which can also plug directly into the laptop. I've noticed that the 90W supply charges the laptop faster, but I prefer it mainly because it has a much longer power cord.
The efficiency figures Ranger has hypothesized are not necessarily accurate; it depends on the design of the specific power supply and the optimal load range. A given power supply may be more efficient under your own typical usage scenario, but the only way to find out for certain is to test each power supply's power draw yourself under different loads. For example:
- Plugged into the wall, but not into a laptop
- Laptop fully charged and turned on (idle)
- Laptop fully charged and maxing out power draw (e.g., transcoding video while burning a CD)
- Laptop charging but turned off
- Laptop charging and turned on (idle)
- Laptop charging and maxing out power draw (e.g., transcoding video while burning a CD)
You may find that the higher-wattage power supply is actually significantly more efficient under a high load than the lower-wattage power supply, because it is not near its maximum capacity. In fact, you may find that the higher-wattage power supply is more efficient across the board, and the lower-wattage power supply only beats the bigger supply under a narrow range of loads. Or perhaps the smaller supply is never more efficient, and its only advantage is its smaller physical size.