There's not really a difference if you meant performance wise. The reason why they came with difference wattages is based off the power supply requirements for each model. If you buy a laptop adapter that is 65W for a 45W laptop model, there is a chance you can blow the PSU, or cause harm to other components because it exceeds that PSU wattage limit
But if the adapter is at a lower wattage than your laptop rating 45w on a 65 w laptop, the system might not boot because it requires more power.
More details here:http
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