I have both QSI and Tsunami in both steam and diesel, and I prefer the Tsunami in diesels, and QSIs in steam engines.
I have the QSI programmer, and can program the sound files in any V7 and newer QSI decoder. I am a very popular guy at my MRR club... As a gag, I loaded an "ooga" horn in a Trainmaster, but I digress...
You can do a lot more with a QSI steam decoder than you can with a Tsunami steam decoder, but it does require learning what to do, both with CVs and programming, and how to use it "on the road".
Meddle not in the affairs of dragons, for you are crunchy, and taste good with ketchup.