I've been using a digital tanpura for both practice and performance for a couple of years now, and it's proven to be a reliable investment. I started with the Radel Dhruva Nano ZX, which is quite popular for its compact size and quality sound. It's been incredibly user-friendly with presets for different ragas and the ability to save custom tunings, which is a huge time saver.
In terms of sound quality, these digital versions are getting impressively close to an acoustic tanpura. The Radel model, in particular, offers a richness that supports vocal or instrumental practice quite well. However, I'll admit there's a slight nuance in the resonance of a traditional acoustic tanpura that the digital ones haven't perfectly captured yet.
Durability-wise, my Radel hasn't shown any issues, and it's been pretty resilient on the road. The portability factor of digital tanpuras is a game-changer, especially when you possess limited space or you're traveling frequently.
If authentic tone is crucial, digital tanpuras do a solid job, but they might slightly miss the mark compared to traditional ones. Nonetheless, for convenience and reliability, they are certainly worth considering. If possible, try one out or listen to some high-quality recordings to see if it meets your expectations.