I also chose the Casio PX-150 for my portable keyboard (current model is PX-160), but I use it only to control the standalone Pianoteq software. I switch among Pianoteq instruments or presets between songs only, not in the midst of a song, so it is easy enough just to switch these on my laptop, to keep things simple. For the most part, as the pianist in jazz bands, I use a single acoustic piano preset, without switching presets or instruments. In this role, the Casio PX-150 has been fine. The pros and cons of the PX-150 have been much discussed in other threads, but for me the relevant features are its light weight (11 kg = 25 lbs), low price, and relatively good action. It initially bothered me that the keys bottom out on rubber bumpers instead of felt, but I've adjusted to that.

Of course, I'd prefer a portable keyboard more like my acoustic piano, with longer-pivot (wood?) keys and a heavier action, but currently that would mean greater weight and much greater expense.

I'm very pleased with my Casio PX-150 as far as playability is concerned.  Pianoteq voice must be controlled from the computer.  In other words, all the Casio does is provide the MIDI note data out.  No ability select presets from the keyboard.  Plug in a USB cable, and it just works.  Audio reinforcement is from a separate speaker set not internal to the Casio which is a bit of a bummer as it's just more excess gear.  I'm pretty sure the PX5S has the same action as the PX-150.  I also have a PX-130 with the same action, that I could sell.

I think the PX-150 has some improvements over the PX-130 in the action, but I can't recall. A few other improvements that come to mind are the wood textured keys and the high resolution MIDI.

I am so happy with the Casio PX-350 as a controller for Pianoteq. The PX-150 would be just as good. The PX5S would be preferable if you want to utilize the keyboard's sounds and not just use it as a controller. If you want to do quick transposes via keyboard, I wouldn't recommend the PX-150. Transpose is effected via pressing a button and then a piano key. This isn't good for gigging.

I am looking at Roland RD64(small keyboard - hum), SS-990 Pro, Acuna 88/73,and Numa compact? (Difficult to find any store near Portsmouth that stocks Studiologic). The Kawai VMK188 is near 30 kg.

And I see some people recommend Casio Privia PX5S.

And Kawai ES - 100.

It seems like plenty of people have asked this question previously. I had better do some more reading.

Is it possible to use controls on the keyboard to select different sounds in Pianoteq?