We went to the RV Supershow in Tampa yesterday and all the 5th wheels we looked at had the island in the kitchen. We think that takes up too much floor space.
We've had three fifth wheels, two with islands and one with the "L" counter/cabinet config. We like the extra counter space the island provides. Walking around the island isn't an issue for us either. Islands work for us, maybe it doesn't for others. It's up to the owners, whatever works for ya.