If a future Apple phone has 3D, then iPhone lovers will go for that, Android lovers will go for the Evo 3D or the LG Optimus 3D or other future Android 3D phones. Some will choose after careful comparisons, some will choose as camp followers.
While I respect Apple and what they've done with the iPhone, I'm likely to choose the Evo 3D as just a camp follower - I really like my Evo, I'm all for Android, I don't want to join the Apple ecosystem with my phone - I'll just go with the Evo 3D on the basis of it being better than my Evo (and fiddle around with 3D just to see what's up). I've used the iPhones, they don't interest me.
People may choose an iPod with 3D and an Evo 3D for the same reason that some people choose regular iPods and Android phones even though both play music - maximum flexibility with their personal electronics for whatever jobs they want done.