There is no single photo app under ios8 that can match iphoto for ios7
I've used iPhoto on my iPad and iPhone since it was first available. All my photo editing was done with that one app. I've since upgraded (unfortunately) to iOS8 and tried every standalone photo app looking for the same capabilities I had in iPhoto for iOS7. NO APP HAS THE EFFECTS AND BRUSHES OF IPHOTO. Not Lightroom, Snapseed, Pixelmator, Camera+, Photogene, ... Nothing!!
When Aperture (I use it on my iMac) is gutted like iPhoto for iOS7 and all Apple photo apps becomes Photos, I hope the best of both is incorporated into the Photos app. If not, one of the core strengths of Apple, I.e., graphics and image handling will be lost.
iPad (3rd gen) Wi-Fi + Cellular, iOS 8.1.1