Processor: fast dual-core
For Windows Phone 7.5 manufacturers had the option of exactly one processor, and that was the single-core Snapdragon S3 from Qualcomm. Different versions with various clock speeds were available, so performance therefore did vary from model to model. Still, the market for Windows Phone 7.5 was not very exciting.
Thus far the same can be said about Windows 8. While WP8 in theory supports multi-core processors with up to 64 cores, the initial models all use the Qualcomm Snapdragon S4 processors. These Qualcomm processors have Krait cores that perform quite a bit better than the Cortex-A9 cores that are used in virtually all other ARM SoCs. Both the HTX 8X and Lumia 920 run on a dual-core processor with a clock speed of 1.5 GHz. In terms of pure processing power they're slightly below devices with a Tegra 3 or Exynos 4412 chip, but this is barely noticeable in practice.
The SoCs aren't identical, however. HTC used the MSM8260A chip, while Nokia used the MSM8960. These have the same processor cores running at the same speed, and the integrated Adreno 225 GPU is also identical. The difference is in the modem functionality. The HTC MSM8260A has 2G and 3G, while the Nokia MEM8960 also has LTE functionality. According to the specs from Nokia, the Lumia 920 LTE is compatible with 700, 800, 850, 900, 1700, 1700, 1800, 1900, 2100 and 2600 MHz bands, which means the Lumia 920 should be compatible with 4G networks.
Another advantage of the Lumia 920 is that it has 32 GB of internal storage, compared to the 16 GB of the HTC 8X. Both phones have 1 GB of RAM. Neither smartphone has an SD card slot.
It's also possible to wirelessly charge the Lumia 920. We were not able to test this feature because we don't have a loading station.