Check out clavintejunkie YouTube channel, the guy is a bit arrogant and has terrible taste in music but he really knows his stuff. He's one of the few bt speaker reviewers I actually believe. Head and shoulders above any big website reviews. Recently he's been more into bt headphones but he's reviewed an absolute ton of speakers. There is also a link from his channel to an online sound comparison tool, many many speakers recorded under same conditions and you can switch between them.
UE outdoor speakers are very rugged, good build quality and go really loud, less bass and a bit thinner sounding than many others of a similar class. Still sound good though. I've got loads of bt speakers. Of the waterproof/rugged type medium size I like my Tribit stormbox (formerly known as xboom). Can be had for £50 when it's on sale at Amazon. Well built and competes with more expensive speakers soundwise. Things have moved on really quickly with bt speakers, I probably wouldn't look too hard at models older than 2-3 years. Also you can't really go by brand alone, various iterations of the same speaker, let alone different models of the same brand can be a hit or a miss sound-wise. They're not outdoor speakers, but just in case you consider Denon I would avoid. They can sound amazing but many of them seem to have terrible battery problems, mine included.