as mentioned before its more a decision about the Eco-system you move in. But as you have already a Mac and iPhone 4 I also would suggest to get an iPad. If you care about technical specs like quad-core etc you would need to wait (maybe) until April next year.
if you want/need a tablet now get an iPad; the internal storage with 64 GB it gets you quite far for regular use.
if you want/need a tablet now get an iPad; the internal storage with 64 GB it gets you quite far for regular use.