I've got to say that as much as I love ESU LokSound's diesel sound decoders, I'm underwhelmed by their steam offerings. The Big Boy file that I used in my Challenger is OK on chuffs, but I think the whistle and bell leave a lot of room for improvement. The "steam collection" file I'm using in one of my Berks as a test bed can't hold a candle to the Tsunami Heavy Steam sound that is my "standard" in the rest of my Berk fleet (although, jeez, it really is time for Soundtraxx to add the "open cocks" startup sound to its steam lineup), and I like being able to automate the steam release when the engine comes to a stop, which I can do with the Tsunami, but can't with the ESU (at least, I haven't found a way to do so). So while I think ESU's diesel decoders are far superior to anything from Soundtraxx, when it comes to steam, I think ESU lags far behind.
If ESU wants to play seriously in the steam space, they should go out and do new recordings of our active steamers: the FEF, the NKP 765, the SP Daylight 4-8-4, the Challenger, the Pere Marquette 1225, and the host of smaller steam locos running on tourist lines. Do new recordings of every steam whistle still out there - borrow 'em from museums, or find good sound recordings and digitally enhance them to modern standards. The N&W J may be back in service soon, the UP Big Boy will be eventually, and there are probably good recordings of the N&W 1218 from its operational days that could be used as well.
I know this is asking a lot, but right now I just don't think ESU's steam sounds are competitive. And with a new generation coming from Soundtraxx, they might finally get motor control right, in which case they would be my preferred option on steam.
John C.