I think the value is mainly one of convenience. Sometimes the park laundry might not be available when you want to wash, then you have to watch the time and get back over there to move from washer to dryer, then again to get out of the dryer and hope there is a decent/clean place to fold. With the onboard units, it is much easier to work the chore into other things you want/need to do.
If a full-timer or heavy traveler, I think it would be worth it, maybe not so much for weekend warriors. Didn't know they now have 240V dryers. I'd definitely go that way if I had the choice.