I have a Yamaha Motif xs-6 61 key.

Why 61 keys?

(a) I didn't want a board the size of a surfboard.
(b) the motif xs 6 61 key has different key structure than the 88 key motif. The 88 has weighted keys which if you like to play fast riffs at times is a tad clumsier than FSX keys. I like them as fast as I can get them without sacrificing quality.I dislike totally weighted keys.

However....for a concert or gig performance where you don't want to stop in the middle of the song to transpose or jump octaves, then a 71 or 88 would be the answer.
I don't gig. I write and structure songs etc.at home. So if I have to stop and transpose etc. it's not a problem for me.
But I wouldn't want to be doing this in front of an audience.