I called it an upgrade as the fluke sounds better than the flea and is more expensive. You're right with the terminology however. It's not upgrading necessarily between a soprano and a concert unless of course you have a crappy soprano and are looking to buy a better quality concert. Actually that's kind how I feel about the flea and fluke. Neither instrument I'm that impressed with (unless I were comparing plastic instruments) however again the fluke sounds much better than the flea in my opionion and is worth paying a little more for.
The "in my opinion" is the key phrase there. Glad you put that in
Just got my Concert Tiki Flea back with its new Rosewood fretboard and Aquila strings. It showed up on my doorstep literally an hour ago, and even when playing as the strings stretch out, it's sounds great! I prefer the sound of the Flea to the Fluke. As "non wood body" ukes go, the Flea sounds better to me, and is, in my opinion
a great, all American made, first Ukulele.
I had an experience at my first Uke Club similar to this conversation. An older gentleman walked up to me and asked to see my Flea. He gave it one strum handed it back and said "They all sound the same." and walked away.
By his actions, I'm guessing he wasn't saying it as a compliment, but hey, you get a Flea or Fluke, you know what you are getting: a solid instrument, with dead on intonation that can handle some abuse, and is a joy to play.
All that being said, (written) I'm looking at a solid wood Ohana or Kala for my next mid range ukulele purchase, and I'm dreaming of a Koaloha...
JT