Like you say, Noel, it's comes to which personal preference.
As I said, Mr Soundguy's sound recordings are probably the best available, but I'm swaying towards the Loksounds. The main reason(s) for this is that I prefer the way the Loksound "drives". The hard acceleration is very good, you turn the throttle rapidly up to notch 5 and the engine sound goes straight to high revs (around notch 6-7) then settles back down to notch 5 once it reaches that speed. The ability to notch up or down with the function keys independent of speed is also great. There is also a brake and acceleration function which I have yet to get to grips with.
Also, now that I have a Lokprogrammer I can download my own files from the ESU website and customise each loco; different engine, horn, brake sounds etc. can be programmed to each loco. All functions can also be remapped as I choose.
That's the reason I'm selling the MSB decoders, to fund more Loksounds! Having said that I still have one of each the 141, 071 and 201 chips from MSB that I will hang on to, the 071 and 201 in particular are very good.