Of course Apple Pay will only be available to Apple users. That's literally what Apple Pay is: contactless payment on an Apple device. There's no reason for there to be Apple Pay on Android or another platform.
If banks have their way, there will be no ApplePay, no AndroidPay etc
It's quite clear which one is better.
The unified system supported by all banks and all devices?
Yes a unified system on which Apple, Android, or whomever wants can develop a system that is open to all to use.
Both Apple and Google want to keep Apple Pay and Android Pay exclusive to their platforms.
That being said I have still the choice to way I pay and that won't be different than when ApplePay is available... . If I heard it correctly it can even use the same POS HW that other NFC based payment solutions use.
The only "negative" thing will be that I as a consumer, will have more choice.
Although they did announced Apple Pay on the WEB. It will require Safari - which is available on iOS/macOS exclusively.