What's the appeal of the $100 Outdoor vs the $50 Waterman?
IMO, just about everything. I like the build and the sound quality better. Not that the sound is outstanding, but it's good. It's a heavier, sturdier instrument. I didn't care for the first generation model of outdoor, but with 2, they fixed the things I didn't care for.
1) Design. The Outdoor Ukulele (current models) were supposedly based off of the measurements from a well respected ukulele builder. As a result intonation and set-up are very, very good.
2) Sound. Waterman, Bugsgear, and Woodli ukuleles, made of ABS, have a plastic sound. Some Waterman are okay—others have been atrocious with intonation and action. The Outdoor doesn’t sound as if it is made of wood, but it does sound different than the ABS ukuleles.
3) Durability. The Outdoor can withstand 240°F to -40°F. Waterman and Bugsgear have a very attainable point (in the sun in a hot car) where they can melt.
@Jerryc41, in short, everything.
I have played both now for a a fair bit (meaning, longer than going into a shop for a couple of minutes). The Kala Waterman I had was ATROCIOUS! I mean awful. The tone was terrible but it was the action that made it virtually unplayable for me. It was so high that (I'm not kidding or exaggerating), when you'd fret the strings they would no longer be in line in front of the sound hole and it was nearly impossible to strum every string consistently. You could clearly see this if you looked down across the strings in front of the soundhole. It drove me mad and really, really frustrated me. I was worried that it was my playing but would tell myself it wasn't. It was also terrible in that, the notes were so "off" (likely because of the action?) that I couldn't tell if certain chords were correct or not. I even tested it with a tuner. For instance, once I got the strings in tune for that playing session, I could play the open "C" string then play the "A" string fretted to "C". It should be an easy octave apart. But it was so "off" that the tuner read it almost going past C#. Also, it wouldn't stay in tune. I'm not just meaning during the string stretching phase, as expected, but in the nearly month that I had the chance to try it, I couldn't keep it in tune for as much as a day, sometimes less. Also, I tried things like playing "D" (2220) as a partial barre chord, rather than 3 fingers together and it was completely impossible. But I didn't realize why till I received my Outdoor Ukulele.
In contrast, the OU is fantastic. The action is so low, it's mind blowing. By far, it's the easiest uke to play of any I've tried (and while I'm no expert and still very much a newbie, I have taken the advice of these forums and gone to my local music shops to play as many ukes as I can, which has been quite a few). It takes less pressure on the strings to get the perfect ring and the strings are perfectly in line in front of the soundhole when fretting. So, the issues I was having with the Kala, completely disappeared on the OU and suddenly, the songs I had been struggling with due to missing strings while strumming, I could play without difficulty. The notes down the fretboard are perfectly in tune so unlike the Kala where it was very sharp, the OU is dead on (again, checked with a tuner). As others have mentioned, while the OU doesn't sound exactly like wood, it doesn't sound like plastic either. I think it's because of the way it's made. The polycarbonate they use has either glass (standard) or carbon fiber strands inside the poly to give additional rigidity. But, what this also does is effectively, give it a "grain", similar to wood. So, I think it has more resonance for that reason. It is definitely stronger, more durable, and much better built than the Waterman. You can feel it.
I actually have one of the carbon sopranos (from what they told me, it was the first one ordered, kinda fun!). I do feel I can hear the difference in the "brightness". In fact, if I were to have been asked, I would have said it's more than 15% brighter than the original. It's just slightly lighter weight than the glass filled (with two strap buttons, it is exactly 15oz). I'm working on a more comprehensive review to share.
When comparing things, I try to objectively look at the items and ask, "is the $100 item 2x better than the $50 item?" Often, it might not be. In the case of the OU vs Waterman, I would say it's much more than 2x better. Playing the Waterman, I absolutely understood why people say not to get too cheap of a uke to start with. If I had to stick with the Waterman, I would likely have quit. It was just SO frustrating to play. I was surprised because I thought it would be great from some of the reviews I had seen. In fact, I wondered how much difference I'd see vs the OU but they are worlds apart. Hope that helps!