Many of the URC remotes are much more programmable and would allow you to create a set of buttons that could control both without switching modes. A bit longer to set them up but basically the sky is the limit as to how you make them work.
I'm not familiar with the higher end Harmonies but maybe the ones with the LCD screens would allow you to do the same.
Either way, you definitely want to invest in a model where you can change the onscreen labels of some buttons (or touchscreen.) Then it is as intuitive as you choose to make it.
The above workarounds will work as well but when my Dad, who still refuses to get a bank card, comes over and intuitively knows how to watch TV or listen to the radio, I took some pride all the time I invested into my remote setup.
