If you pick up an iPhone 5s, when they announce their new iPhone in September / October time, your phone will be devalued. This is true of buying a phone at any point in time as they're also bringing new models out, however we're obviously getting pretty close to September. If you wanted to wait, you could probably pick up an iPhone 6 for not a great deal more than you would be picking an iPhone 5s up for now.
I'm an iPhone fan and always found them the best for making calls and general use, they're restricted with some features so i can see the argument against them. I've also used Motorola's, Lumia Phones, Samsung's and LG's but i always head back to my iPhone. I would however love Lumia's if more people had them and developers gave them more love, but i guess that won't happen until more people start to use them, so i'm partially to blame for that, much as anyone else who doesn't have one due to lack of certain apps and development. They're great to use.
In response to Azzi, i'd probably say iPhones are the best device for repairs. They're usually cheap for 3rd part repairs and if you do have an issue that is covered by warranty, it's usually a quick trip to the Apple Store and you'll get a replacement device at that point in time.
Just my opinions, although like stated before, it's all personal choice and one person loves HTC, another loves Lumia etc.