I have worked with DD and have some DA laying around. The UPDI is a very nice and simple programming interface. All that it takes is a USB-UART and a diode or a resistor (I used a diode) to connect between RX/TX.

I didn’t used ATmega a lot, but comparing the experience to MSP430 and EFM8 the AVR chip has a bunch of niceties, superb documentation and life improvements like, in order to clear some registers all one need to do is write 1 instead of the whole =& ~(REG | 0x8) (or something like that, it’s been a while since I write embedded C)

The other thing that I loved is that one can download headers for the chip directly from the manufacturer!

Way too many chip manufacturers keep locking headers/libraries behind their proprietary IDEs, but Microchip, even though they have an IDE let’s you download the headers so one can use whatever tooling one is comfortable with! Props to Microchip for that!!