R7800 is great, works well with SQM (using cake), is easy to flash and also has an easy TFTP recovery mode in u-boot, which makes it really easy to unbrick the device in case some experimental settings brick the device. (Easiness of flashing & unbricking/recovery is often overlooked when selecting a device, but in the long run is is important for anyone who is regularly flashing/tweaking the device.)
If you select R7800, you might get some hints from my community build: