Bad idea if you're leaving iPhones, since Apple products are known to last longer than most Android counterparts.
Anyway, there's a lot of factors that can influence your choice. If you want phones that feel premium and low price-to-hardware ratio, then I would recommend you to two 'N's'. And since you're coming from an iPhone, you better follow my reasoning.
The first 'N' is the 'Nexus 5'. For $350 (16 GB version) to $400 (32 GB), you'll get an Android phone with the fastest Qualcomm processor (Snapdragon 800) and an above average 8 MP camera with OIS (to counteract shakiness) and HDR+ (an enhanced algorithm for producing more sharply-detailed images). The Nexus 5 is fast and without lag compared to other Android smartphones (except probably for Moto X) because other manufacturers like Samsung and HTC customize the UI (user interface) of their phones and add a lot of their apps (called 'bloatware') that run on the background. Nexus phones and tablets do not have such bloatware except for Google's apps which are generally used by people.
Another reason for choosing Nexus 5 is its similarity with iPhones in some crucial factors. The Nexus 5 has non-removable battery, non-expandable storage and pure stock Android OS which makes it updated regularly when Google releases a new version of Android (just like iOS). For non-Nexus smartphones, updates come directly from the manufacturers since they will still integrate their UI skins and bloatware with the newer version of Android.
The downside for this phone (compared to iPhones) is its built, which is not made from aluminum but is not easily breakable either. If you want, you can buy shock-absorbent cases and screen protectors to further protect your device. And if you're going to use it on games heavily, do not expect it to last longer than a day. But on moderate use, it can definitely last for more than a day.
I own a Nexus 7 tablet btw, and it's fast even though it has a less capable processor than Nexus 5.
The next N is 'Nokia' (especially the Lumia series). The Lumia series has been rising on the low-end smartphone market since they are durable and run smoothly even for a low price. Their high-end phones are even better especially those embedded with the PureView camera technology. Nothing comes close with Nokia Lumia's smartphone cameras compared to Android phones and iPhones at the same price range. I own a low-end phone, the Lumia 625, and it's decent enough for video recording (it can record 1080p videos), picture-taking (I think it's 5 MP camera is better than most 5 MP cameras on the market), SMS and chat. The Message Hub integrates your SMS and FB Chat into one app, and you can easily switch between the two. The People Hub and the Me hub integrates your FB and Twitter notifications. In terms of social networking, I can use it with a breeze. You cannot expect it to run high-graphics games, btw, but you could expect higher-end Lumias (like 920 and 925) to run favorably with games. You can also link different email addresses into one inbox. And HERE Maps is as efficient as Google Maps.
The downside with the Lumia series is its OS, Windows Phone. If you are used with Google services such as Google+, then you'll probably get a hard time using those. Even when transferring my OneNote documents using my Nexus 7 synced with SkyDrive, I'm having trouble at it.
So that's it. If you want a wider range of customization, very high-end graphics games and does not care for battery life, go for the Nexus 5. But if you're content with almost limited (but sufficient) number of apps, a very good shooter and battery life, go for the Lumia series (920, 925, 1020 or even their new phones, 1320 and 1520), whichever you can afford.
And don't be like others who complain with their phones. Each phone has its own pros, limitations and problems. You can solve most problems with just a few browsing (like what I did). Focus your preference on what do you think your phone's function would be in your life, then learn to live with its limitations and explore a lot to find its pros.
Experience; I read a lot of tech blogs and websites daily