Using a HP adapter on a Dell could cause minor issues, most Dell bios communicate with the AC adapter (dallas chip in the AC adapter), so it will not recognize the HP adapter, it is possible it will not allow charging of the battery due to this, it will however power the notebook, all you can do it try it.

The output volts and amps are so close that is not an issue.

Using a HP adapter on a Dell could cause minor issues, as most Dell BIOSes communicate with the AC adapter (there's a Dallas chip inside the adapter), so it will not recognize the HP adapter. Thus, it is possible that it will not allow charging of the battery.

It should, however, power the notebook.

The output voltage and amperage are so close that is not an issue.