Product Differentiation is a WIN WIN 4 Apple
The iPhone 5c has created product differentiation in the iPhone lineup... and perceived value evermore for the 5s now and the whole iPhone line up altogether in just a matter of time.
This helps the 5s initially, and helps the 5c create its own market in due time. And, I do predict these C's will be flying off the shelves around the world by the "6c" update debuts. Or, especially, when the 'C' gets biometric scanning(Touch ID) and now the low-end product isn't so "low-end". Give the 'C' 18 to 24months to capitalize its market...
When the iPhone 5c has found its true customer base, I'd say within a year to 18months(or right after the next update) maybe less, the 5c & 5s will be selling strong, and Apple's brand will be more global because of the marketing stance they are taking now with the 2 models.
Ultimately, the 5c is one of the smartest moves by Apple in a very long time... just give it 2yrs and both models will top their given/respective true market opportunity. And, when the Touch ID debuts in the next iPhone 'c', suddenly... this low to midrange smartphone is now perceived not so low or midrange.
So, Apple has more room for marketing strategy for both the 5c & 5s(the whole iPhone lineup), and Apple 3rd party co's win, but we/consumers may lose on certain updates intrinsically(not as good specs) even though now, due to product differentiation - we, the consumer, will never get the feeling we lose... we just have another option, and the cheaper option, may one day be a good option or cost-effective option nonetheless.
One day, I could see myself going to the 'C' over the 'S' just to be a smart cost-effective Apple shopper... even though most Apple customers, want the "best", the 'C' will still be the "new"... and the 'C' will stand for Cost-Effective not colorful from a marketing perception.
Give it time... Apple wins big here, and has started a huge game with Biometric scanning that they will win as well, and just started to pioneer. The leather wallet & D&G purse will go bye byes, and Touch ID will be a very secure authorized payment accepted online or any brick & mortar store across the world.