OLED IS awful. Here's why:
1. Extremely poor color reproduction
2. Extremely poor visibility under sunlight
3. Awful sub-pixel structure that results in grainy text even with fairly high pixel density (it's not a simple RGB per pixel type of thing)
4. Very low brightness
5. Poor viewing angles
Most of these (exception is 2) are the polar opposite of IPS/LCD characteristics. Why IPS is the best, OLED is just the worst. I saw a post above that stated not all OLED screens are made equal. That is perfectly true. But overall, LCD is much better. Forget the negligible power savings of OLED, it doesn't make enough difference for anyone to notice. Of LCD panels, IPS is the best. It's not surprising Apple uses the best (metal, glass, IPS, etc.) while Samsung uses the worst (crappy/creaky/cheap plastic, OLED, etc.).