It was a truly genius way to go about it by apple (see the play : ). I think since you plan on getting a iPad and already have an iMac I would lean towards the iPhone, aslong as it's not a old mac as then next year you'll be in the same situation where you are forced into buying another Mac PC because you already have the iPhone and iMac...
I guess I'm not getting it because both features sound about the same to me. The only difference appears to be that you add whatever you are looking at to your read list on your iphone and then open up that list on your mac, whereas on an android, you just press the sync button on the laptop and it will display whatever webpage you have open on the android and vice versa. Bookmarks automatically sync together. Either way, go with what works for you.