Switching from iPhone to Nokia Lumia?

First of all sorry for my English, I'm not a native speaker!
I have been using my iPhone 4S for almost 2 years now. I really love it, but with iOS 7 it's a bit slow because of the 512MB RAM (eg.: it has to reload the webpages everytime I press the home button and then go back to Safari).
Yesterday I tried out my friend's Lumia 925, and I loved it. It's really fast, and the camera is amazing. The AMOLED display is a bit weird, compared to my iPhone's IPS, but it's not bad.
I'm thinking about switching my iPhone to a Lumia 925.
What do you think? Should I switch, or should I stick with my iPhone 4S?
Thank you in advance!

Added (1). Actually the store is full of apps. Facebook, Instagram, Snapchat, even games like Asphalt 8 and Modern Combat 4. And that's all I use.
The 8.1 update is coming soon (end of June), my friend has a developer account, so his phone already got 8.1, and I think it's really awesome.
But if you say I should stick with my iPhone, then I won't switch.

If I'm correct, the Lumia 925 is running windows mobile?

You won't find a lot of popular apps on the Microsoft marketplace… That's a major drawback.

Most popular and common apps are available on iOS or Android… Also, there won't be much support from 3rd party developers on windows mobile.

Nokia limos is not very good compared to iPhone or android phones. There are better options.

No, its a windows phone, and windows phones don't support as many apps and things like that as the iphone, and android, if i were you i would swich to android, but i would rather stay with an iphone than swich to a nokia lumia

Nokia is great but windows 8 will take some time to get used to because Apple's IOS is the easiest of use of all others, but the battery life and customization is terrible on it and iOS 7 is the best on i Phone 5 versions
i Phone 4S on the other hand is old by now you may want to switch to nokia if you liked it but take your time and test it a little if possible or save up for i Phone 5 or 5c If you like i Phones. I Personally have i Phone 5 because i didn't try any others beside android and i didn't like it and also windows store don't have many popular apps you may check windows store first on the internet to see.

4S is actually from several years ago, there have been 3 iphones released since then so your hardware is a little outdated. Its worth $199 on trade in still though:
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Apple also recently boosted the trade-in values for the iPhone 4 and the iPhone 4S. Apple Stores now offer up to $99 toward a new device for an iPhone 4 and up to $199 for an iPhone 4S.

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