The average used prices here in the USA...The MZ2000, $500-$650[very hard to find]..
The PSR3000 $1,200,,easily available..

I agree with Squeak's comments..I would like to add..The MZ2000 has a better key feel and full size keys..It also has great control of inputs for other sources[laptop] that can be assigned effects.

The draw bar organs and Leslie effects are superior on the MZ2000..The piano with slight edits are better on the MZ2000.
The MZ2000 is more playable to me...comfort wise , keys and association to the sounds.

The MZ2000 speaker system is also better than the PSR3000..

The PSR3000 will give you a vocal harmonizer, not available on the MZ2000.

Caution on damage to any keyboard...If they are giving you a real guarantee on the Casio, you may be okay..

Repairs and parts availability go to the Yamaha..

Dollar to dollar..here in the USA or where you are....the MZ2000 would be my choice....besides the MZ will probably retain most of it's current value...the PSR will not..