There are very diferent instruments and sizes, it will be more fear to compare the PA50 to the EXR5....even in price should be the EXR7....well, here my own opinions:
1.-Neither keyboard has arpegiator.....they have styles or patterns that are an orchestrated 4-8 bars with drums, bass, piano, etc...depending what style is playing.
2.-For what you say, I understand that you want accompaniments, well there are two ways to achieve this, A).- Using Midi Files (secuences, SMF)....B).- Real time accompaniments...
3.-In both brands you can download and or buy styles/patters ( USB company in France that sells CD with 1000s of styles for any keryboard brand).
I hope it helps.

Manuel

Alexx...yo tengo el PA60 que es identico al PA50, la diferencia es que el PA50 es manufacturado en China, los 2 teclados son muy diferentes, Aqui, en Phoenix Arizona, El PA50 y el EXR7 se venden por mas o menos lo mismo $999.00 dls. Yo te aconsejaria que checaras cuales estilos/patrones ritmicos de fabrica te funcionan mejor a TI....porque a los 2 les puedes poner estilos ya sea bajados del interner o comprados.

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mdorantes