Loksound Extractor 13 __EXCLUSIVE__
On the updatable decoder topic, that's a clear win. I haven't used a loksound, but I have used zimo decoders and even though at the time I installed them zimo had better motor control than anything else including loksound, the motor control got better with updates over the source of 5 years or so. No software is perfect, you can always make it better. All other things being equal I'd take a decoder that can have it's firmware updated over one that can't any day. But of course all other things are not equal, so you need to pick your compromises.
Loksound Extractor 13
On the subject of drive hold vs whatever soundtraxx calls their auto notching in response to load feature. From my personal point of view neither is ideal, but I'd rather have the soundtraxx feature. I either way to control the speed and let the sound automatically do the right thing based on load, or (ideally) control the prime mover and let the speed automatically do it's thing based on load. Neither loksound or soundtraxx can do the second (as far as I know) - I think having to fiddle with the drive hold button would destroy the illusion of running the loco for me almost as much has having to poke buttons for manual notching did when I tried that setup.
if it is KATO, the E235 I was able to find online all use EM13 style decoders. That is a KATO specific form factor though Zimo makes both a regular EM13 drop in and one with sound capability and ESU makes an EM13 drop in version of the loksound 5 I think it is.