Because of Microsoft’s strict chassis requirements, Windows Phone devices cannot really vary a lot in terms of internal hardware. And because of the slow pace of updates for the OS, it usually takes a bit of time before devices running this platform can match something like Android flagships hardware for hardware. With the GDR3 update, Microsoft enabled support for the new Snapdragon 800 SoC and 2GB RAM devices along with full HD displays. Since Lumia 1020 came out before GDR3 was announced, it runs previous generation hardware.
The phone is powered by a Qualcomm Snapdragon S4 SoC. The chipset model is MSM8960 and it includes dual-core 1.5GHz Krait CPU with an Adreno 225 GPU. There is also 2GB RAM, of which 1GB is reserved for the OS and the remaining 1GB is for the camera. On paper the hardware is decidedly outdated. This is close to what we saw on Android phones over a year ago, which have now moved on to newer and more powerful chipsets. The truth of the matter though is that Windows Phone has never really been a resource intensive OS. Even with the supposedly old silicon, there was practically no lag anywhere in the OS. Apps opened quickly enough and I was able to navigate the OS without any hiccups at all.
However we cannot completely discount the advantage of using newer chipsets. Lumia 1020 does not have support for WiFi 802.11ac, which is becoming increasingly more common in phones. It also does not support faster LTE (150Mbps) due to its older modem. The new Lumia 1520 has support for a pedometer right on the glance screen, also something enabled by its more up to date hardware. Similarly newer chipsets also tend to be more power efficient.
Battery on the Lumia 1020 is temperamental to say the least. I’ve had similar experience with the Lumia 920, and it looks as if nothing has changed with GDR3. Overnight it can experience battery discharge of up to 10-15% in just 8 hours. However the next night it’ll discharge only about 2-3% overnight. Depending on your use you may get close to a full day’s worth of battery life. However if you take pictures or play games, you’ll find yourself charging the phone again before the evening. There is also no built-in wireless charging. Nokia instead moved it onto an external case which is sold separately. This was done to reduce weight and thickness, for which I’m thankful.