The Megaboom 3's battery life is a whopping 20 hours

https://litecomparison.com/ue-boom-3-vs-ue-megaboom-3/

When I was working in my garden one day, I had mine on full blast for four hours and still had 20% charge left, unlike one fellow who had his on full blast for tailgating and it cut off after three hours. I've also used my Megaboom 3 at lower levels for over 6 hours and still had energy left over. Maybe it's a combination of chance and skill, depending on how well your battery was made and how and when you recharge it??? This can only be correct if both speakers are mono and the signal created by the source conveys the picture to both speakers, resulting in a'real' stereo image. Otherwise, just one or two speakers will give you a stereo sensation, and none of them will be mono. They blended some instruments panned to one side (mono) and then the opposite side (stereo), extending the sound stage like an old record from the 1960s and 1970s. It may appear more difficult than it is, but you will not receive a (stereo) sound with two speakers unless they are MONO speakers.
Yes, the UE Boom 3 has a somewhat richer and clearer sound, especially when using the EQ on the Boom app. However, you are free to wait till the UE Boom 3 is out. The UE Boom 3 is a touch bigger, and it can be charged with a separate Power-Up charging connector. It also floats in water. The bluetooth connection, in my opinion, is the device's weak area. It sounds great for its size and price, however the connection on the one I bought can be problematic.
Megaboom 3 is waterproof and engineered to continue booming even when wet. It has an IP67 water and dustproof certification and can be totally submerged in water for up to 30 minutes. It can also float. Megaboom's 360° sound is incredibly loud, clear, and immersive, with a visceral deep, thundering bass. Everything has been fine-tuned to ensure that you can hear every note. MEGABOOM 3 is created from a sturdy and stylish two-tone fabric. This is the dish to order if you want to make your mouth swim. It's designed for exceptional performance and comes in two colours.
The Megaboom 3's battery life is a whopping 20 hours. Thanks to the latest cell technology, it will last almost a full day on a single charge. With the POWER UP charging station (sold separately), you can charge MEGABOOM 3 wirelessly and take it on your next musical adventure fully charged. Megaboom 3 is built to last and is eager to go on an adventure. We put it through a series of rigorous testing to ensure that it could endure repeated button pushes, tumbles, and drops, among other things. PARTY UP/SHORT: Use PartyUp on the Ultimate Ears app to pair 2, 3, 4,... and over 150 speakers for the ultimate sound experience. Any BOOM and MEGABOOM generation can be mixed.
The Ultimate Ear Boo 3 is very portable, water-resistant, and nearly instructable. The Ultimate Ears BOOM 3 floats and is entirely waterproof. BOOM 3 was designed to be wet, with an IP67 water and dustproof rating that allows it to be fully submerged in water for 30 minutes. No matter how wild things become, your music will always be on spot. Ultimate Sound: A Bluetooth speaker that delivers 360-degree bold, immersive, crystal-clear sound and can last up to 15 hours on a single charge. No matter where you are, it brings your music to life. New Magic Buttons have been introduced to replace the old ones. You can play, stop, skip, and control any streaming music right on the Bluetooth speaker with a single button click. Create one-of-a-kind one-touch playlists for Spotify for Android*, Music Unlimited, Prime Music, Apple Music, and Deezer Premium with a single click. BOOM 3 is covered in a gleaming two-tone fabric that's tough, beautiful, and designed for tough applications like motorcycle jackets and fire equipment, meaning that this performance textile is weatherproof.