But sadly, when your arranger DOES have a beautiful Grand Piano inside it, it is a crying shame to not be able to stretch out and use it...

Don't forget the humble Fender Rhodes, either (although a little easier to fit into 61 notes). Not to mention the fact that, if you allow yourself 2 octaves for chord recognition, that's only 3 octaves left for your RH. Split THAT 3 octaves to get two lead sounds, and you are into seriously cramped conditions.

Then add in the demands of using the keyboard with SMFs, where you play in a FAR more 'standard' keyboard mode, sort of WS country, and having a decent range for at least TWO important sounds is usually a necessity. Although a 61 definitely takes the edge for 'convenience', 76 is often the more 'musical' choice if you want to PLAY like a normal keyboard player, who either favor several 61's or a 76 or even 88 as their main 'solo' axe.

If you STRICTLY only use the arranger in 'arrange' mode, 61 does the job adequately (but barely, IMO), but the minute you want to stretch out, and use it for sequenced stuff, or God forbid! even play with a band (the horror!), 76 starts to be more useful than inconvenient.

But, as usual, JMO, yada yada yada...