I've got a stay booked for November and faced the same dilemma - we ended up booking the HI because we're going on several day trips out of Shin Osaka and appreciate the laundry option for the price.
I'm waiting for more reviews for voco before I decide but I think IC Osaka is out because of the price. I already feel I was extravagant by staying at IC Beppu...lol... I'm leaning towards HI Shin Osaka for now too and will leave a review after my stay.