Reply to 49 keys? 61 keys? 88 keys?

Hi,

Im currently using the akai mpk mini 25 key controller but its a little to small for playing chord progressions and bass lines and it doesn't have very many assignable knobs. Right now, im believeing of upgrading to the m audio oxygen 49. Is it worth the money to get a 49 key keyboard or should I get a 61 or 88?

Thanks