If you're considering staying in Emke, which is in an alright spot, I would still recommend the apartment
It's cheaper, a lot bigger, and there's something I don't like about Ibis hotels - they're fine and clean but always very sterile and have a lack of atmosphere. The apartment is a bit closer to the Danube, but like in many European cities there's no real 'downtown' to define in Pest - as far as I'm concerned all places mentioned in this thread are in it.