Recent leaks suggest, the Google Pixel 4a release date might be pushed even further due to the current pandemic situation and the phone could be released to July or even August. This delay might seem bad but it could give a tough competition to iPhone releasing somewhere in September. The entry-level iPhone is going to be priced at $649, whereas Google is putting its Pixel 4a for sale at $349.
The pixel 4a is rumored to feature a 5.8-inch OLED display, which would be bigger than the 5.4-inch panel on the entry-level iPhone 12. The iPhone 12 is going to have higher pixels, but not many people care to pay a bigger amount only for the sake of higher resolution.
Google Pixel 4a will likely have 128GB of storage to start with, which is almost double what iPhone SE would have. For some unknown reasons, Apple refused to adopt USB-C for fast charging, the Pixel 4a would have a USB-C port just like its predecessor and 18W charging. The iPhone 12 will reportedly stick with a lighting port. The iPhone 11 was shipped with a 5-watt charger out of the box and there is no sign that this is going to change for the iPhone 12 series.
The pixel 4a will likely to have a primary 12MP camera, compared to the wide and ultra-wide shooters on the iPhone 12. But Google has integrated highly-efficient AI algorithms that do an excellent job of delivering great results even with limited hardware. As per leaks, there will be a small punch hole camera on the front side of the phone. The iPhone 12's notch is supposed to be smaller than the one in the iPhone 11 but it will likely still be larger than the Pixel 4a's cutout.
The rumors suggest that the Pixel 4a will be powered by a Snapdragon 730 processor. This should be good enough for a mid-range smartphone, but the iPhone 12's rumored to have an A14 Bionic chip that is once again faster than any phone. The Pixel 4a would not support 5G networks which means you can't have fast browsing on the internet even when it is 5G around you.
This makes it undesirable for people who value internet speed more than the camera on the phone. Overall, the Pixel 4a is good and if you are a budget-conscious user, this should be your first preference. But if money isn't an issue or you can't live without 5G internet speed, iPhone 12 is your bet.