Adding some recent experience with Ubigi and Airalo eSIMs in Japan. Partner had Ubigi eSIM on her phone, I had Airalo eSIM on mine.

Both eSIM services worked well, however, there were two occasions where the Ubigi eSIM had no data, while the Airalo eSIM had data. One was at the shopping mall in Nara, where our Japan Wireless pocket wifi had zero data, which was surprising because it had worked so well prior to that. My partner's Ubigi eSIM was also completely lacking cell data. I fired up my Airalo and was able to get data, to perform google translate on menus and get directions, fortunately.

Second data point, at HND airport, on the plane, partner's Ubigi eSIM had no data, couldn't pull up some information. I had to hotspot from my Aiarlo eSIM so my partner could get internet access.

Overall, I think I might prefer Airalo over the Ubigi based on my data points, but I would always get a Japan Wireless pocket wifi as that provides unlimited data reliably in most cases, and the phones battery level was far less drained as the cellular mode was off during that time.

I usually use eSIMs when I travel, but the Japan Wireless pocket wifi was life changing in having amazing fast data without having to think about data usage or battery drain.

I did use Airalo eSIM in the UK recently as well, unfortunately the hotel I stayed at was in a dead zone, and I had the weakest of signals possible in the hotel room (the wifi in the hotel was also very poor as well). Overall I think it's cheap enough to have redundancy with Airalo and another eSIM for global travel, so might as well get a backup eSIM just in case one network doesn't cut it.