Thought about both. Haven't decided. I think I would prefer pressure washing but don't want all that water going down onto the floor. I could sandblast the inside and pressure wash the outside. Then again, I've heard that the sandblasting really chews up the wood. I might just do nothing. Need more input.
Sand blasting does not chew up the wood unless the operator gets the nozzle too close or holds it in one place too long. Sand blasting is expensive, messy and requires a moon suit and mask/filtered air.
Pressure washing won't hurt anything, it is no different than your structure getting rained on before it's finished. It's cheap and really messy and does almost as good a job as sand. I have not used Media yet, but like Amstaff says it is a great alternative.
If you do nothing(which is fine) your logs will have that patina on them forever. Only you or Mrs Bo can make that call. I chose to wash mine because of all the dirt/debris/marks/uneven patina(greying) on the logs.
Here is a before and after pressure washed railing log: