Dongle against desktop amp, Bluetooth receiver against player — any two of 53 sources side by side, measured against the headphones you actually own. Output is estimated into your load rather than quoted at whatever impedance flattered the spec sheet.
Once both have enough power for your headphones, extra watts change nothing you can hear — a source delivering four times what you need does not sound four times better, it just has volume left over. What does differ audibly is output impedance against low-impedance multi-driver IEMs, and noise floor against sensitive ones. That is why a $9 dongle and a $500 amp can sound identical with easy headphones, and completely different with a pair of Andromedas.