Tankless water heater

My buddy got one (Furion) with his new RV. Keep in mind that his WH is very close to all the sinks and shower - so he has the best scenario. His complaints are that it takes 20~30 seconds of water flow for it to actually start heating and that it takes too much water flow for it to turn on. So it's very inconvenient when washing dishes and they end up standing in the shower waiting for it to fire up. Both of these result in a lot of wasted water.
He is seriously considering installing a traditional 10 gal WH.