the op-1 has been around way longer and there are 100x more videos with it over the op-z.
I find the op-1 is better for playing the keys, but the op-z is better for sequencing. The sampler on both devices have similar limitations.
If you want to dip your toes in the TE synth/sampler/sequencer relm and be friendly to your wallet look at picking up a couple of the PO line. Grab a po-32 a sick drum synth, a po-33 for a sweet sampler, and one more po synth that speaks to you. I would go for the po-14. You should be able to get each device for undr $100.
I have owned a op-1 since 2011 and never thought about selling it. If it was stolen or broken I would definitely buy a new one at the higher price. I would be mad about it but still would figure out a way to pay for it.