Both CSP models have one button. All of the state of the art features are controlled through your I-pad. The features on the CSP 150 and CSP 170 are identical.
The two distinguishing features are the wood key action and larger speakers you get on the CSP 170.
The CSP 150 action is the GH3X (Graded Hammer 3X) keyboard with synthetic ebony and ivory keytops, escapement
The CSP 170 action is the NWX (Natural Wood X) keyboard with synthetic ebony and ivory keytops, escapement
POWER (speakers and amps)
The CSP 170 Amplifier (45 W + 45 W) × 2 and the Speakers are (16 cm + 8 cm) ×2
The CSP 150 Amplifier 30 W × 2 and Speakers 16 cm ×2
Depending on the skill of the player (or their skill trajectory of the player), the CSP 170 handles a little more like an acoustic grand piano and gives you more control over the dynamic range and breadth of sound.
We have had a number of great players who have gone with the CSP 150 due to budget restraints and the reviews are all positive.
Check on the latest specials on the CSP series at https://myfirstpiano.net/collections/2022-csp-series