Again, go back to - http://www.casio.com/products/Musical_Instruments/Portable/
and check the stats on both.

An arranger will give you auto-chords and rhythm. A regular synth keyboard probably won't do that, but could have rhythm and drum capabilities beyond that of a lower to mid-level arranger. Unless you are sticking with the arranger idea strictly for price purposes, I think a regular synth might give you more of what you're looking for - if I'm reading your intentions correctly.