Iffy on it, personally, if the planet isn't some random fuck-off world in the middle of nowhere.
The chances of people coming up with multiple different names for a given planet are a little too high. Not to mention people giving the same name to different planets. Better to just use the boring one and have everyone know exactly where the hell you're talking about.
Edit - Context is also important. Some planets you'd likely just refer to by the system name and no number and it would be safely assumed you're talking about that planet. For example, people referring to Tash-Murkon Prime are likely to be talking about the fifth planet, even though there are two temperate worlds in the system, given the presence of the T-M Family bureau stations in orbit there and nowhere else in system. Or P6 in Kador Prime, which is the only temperate planet.