Microstation will get away with size and weight( since there is no competition - great practice/smf player/song recoder) as a second keyboard , but pa 50 sd ( year 2000 technology) will start to show yout it's limitations ( terrible keys/ 2 busy fills/not good enough 4/4 simple styles compared to Yamaha) and annoy you as a main arranger and you will want to get rid of it very quickly.
Most will spend $ 250 more and ger S700/710 for excellent style support.Even though Mictrostations limitations are obvious, you will still want to keep it because of it's over all versatility price/weight/size/SMF play/Seq/KB in a band. I hope the sales of Microstation will put Yamaha to make mini S700 for same price wilth full features/outs/2 wheels.