Not to get TOO controversial here, it's just a thought, but has it occurred to anyone that, if you get an arranger with a sequencer built in, AND TOTL piano sounds (or electric pianos) you MIGHT not always be playing in strict arranger mode.

A VERY large proportion of arranger users also use SMFs. Now free up that left hand, and now you actually DO have the potential to actually play a REAL piano part. This is where making the decision to go with a 61 note keyboard may come back to haunt you.

It's not that a 61 isn't probably the ideal size for just playing in arranger mode, most here think it is. But if you DO play piano (or want to learn), it is a shame to get a keyboard with a VERY good piano sound, and then have insufficient keys to use it fully...

JMO, yada yada yada....