Here is the song I wrote for my wife Shannon before we were married, with Fianna's Pat McReynolds on 12-string guitar and me on the Clarke Sweetone: [Shannon's Song].I may be turning into a crusty old man, but I think all whistlers should start with Clarkes, because I don't think you understand why the other kinds of whistle are like they are until you get your mind (and fingers) wrapped around the Clarke.
I like the Clarke original very much, although there is a lot of variance from whistle to whistle. Some are pure-toned and very clean with some resistance, others are breathy and edgy and feel like trying to blow down a rain barrel.
The Sweetone is a perfect whistle for kids and for learners who don't like having the wood of the original model on their lip. Although lots of players have a real aversion to the Sweetone, I think it's an OK whistle. The intonation is good, the balance between octaves is very good, and the tone is clean and a bit chiffy.
The Meg is their latest model, and has the distinction of being the cheapest whistle made, selling for about $3. They are quite similar to the higher-priced Sweetone line (about $8, for the big spenders amongst you!), but seem to have less consistency from whistle to whistle.