I'm sure you'll hear from Booli, as he is kind of the resident Flea/fluke expert. Having played both, and owning a Fluke (tie Die by the way), I feel that the Fluke has a somewhat bigger and bassier voice than the Flea. The Flea sounded more traditional ukulele to me. I found the Flea a bit more comfortable to hold as the bottom edges of the Fluke sometimes poke. Either way, unless you're going to use as a beater (leave in the hot/cold car, play in the beach), upgrade to a wood fingerboard and geared tuners. The plastic fretboard and friction tuners leave a lot to be desired.
aye - checking in here just now
Lots of good advice here already that mostly matches my own experience, and
you might want to check out all of the previous resources where I've contributed to this topic, which are linked to in this post:
http://forum.ukuleleunderground.com/showthread.php?119495-Fluke-advice&p=1829543#post1829543
I have both Flukes and Fleas...currently...and will be selling a TENOR Flea soon, which they do not offer currently on their web site. Last I checked when I spoke with them was that a TENOR Flea was a special order item, but that was over a yr ago and not sure if they still offer it...
I will confirm that the Fluke body has more low-end frequencies than the Flea. I tried low-g on several Fleas and was not satisfied with the sound, whereas low-g on a Fluke sounds nice like any normal wood uke.
Having said that, you CANNOT use wound strings, i.e., wound low-g on one of these with a plastic fretboard as your will chew down the frets real fast, just think of metal vs. plastic...so if your intent is low-G either get the upgrade for the wooden fretboard, or use an unwound 0.0358" fluorocarbon string for your low-G as comes with most fluoro sets.
The Flea 'sounds' more like a pineapple uke, and can sound nice and bright with the lighter Martin M600
concert strings and the Fluke has a fuller tone overall, with more
potential for different tone, depending upon the strings. The Fluke can sound bright OR warm depending upon strings, the Flea is pretty much 'The Flea' and to my ear sounds muted with nylon or Aquila strings (I have tried THEM ALL).
Had I to do-over, after the Lava concert Flea and Koa tenor Fluke, (acquired in that order) as per my linked threads above, instead of getting 2 TENOR Flea next, I would likely have gotten a CONCERT and TENOR Fluke as I personally prefer the sound of the Fluke at the tension of tenor scale, and to me, the Flea, is like it's little brother, and tension and tone on the Lava concert Flea with the Martin M600 strings is crisp, bell-like and very dulcet and easy to play.
Intonation is EXCELLENT out of the box on all of them and the quality control and consistency from one instrument to the next is quite amazing, considering these are built by hand, one at a time by the handful of folks at The Magic Fluke Company, and not by machines on an assembly line in a chinese factory.
Also, if you want an UNDERSADDLE pickup, get the upgrade from MFC at the time of order, for after the fact there's no way to do the install yourself with the one-piece molded bridge, and with the two-piece saddle/bridge you will be drilling holes right into the top bracing underneath and likely will kill the tone.
I have confirmed this with a mirror and having said all that, installing a surface transducer pickup yourself, later on is easy-peasy, but unless your fingers are like 8" long you will never be able to attach the pickup to the bridge plate, but it works well and sounds good placed just behind the top brace that is near the bridge-side of soundhole.
I HIGHLY encourage you to examine the links included in my post referenced above.
Any other questions - I am happy to share what I've learned hands on with 4 of their instruments now...
BTW: Reason for selling the tenor Flea is because I have too many ukes that are unplayed (more than a dozen), am now forced by my CFO to adhere to the one-in/one-out rule (one just came in), AND will be moving soon to a MUCH SMALLER home or apartment. I love the Flea and Fluke ukes, but cannot justify redundancy at this time.