So I have been comparing these two, although not side by side. I have also been comparing them to K-ukes like Kanilea, Kamaka, and KoAloha.
I haven't touched a TK-300g since last Fall, but I remember it being gorgeous to look at. The neck width was on the narrow side, making it easy to get my hands around. It felt comfortable. Tone was not terribly loud, but it sounded sweet.
The Martin, and I have tried two of them, sounds tight. It's not particularly responsive. Once you lay into it, it gets loud, but it doesn't have the richness of tonality or responsiveness that better ukes have. Asking someone in a shop where I played one, he said that the Nazereth, PA built Martins are better, more responsive and richer. But he says they're built like Martins, for bark and volume, in comparison to a Hawaiian uke, which is more designed for tonality and subtlety.
One T1K sample had terrible wood matching. The other one had nicer wood and was much better matched. I wonder about their quality control a bit, regarding ones from the Mexican factory.
I played two Kanileas as well as one Kamaka at the same shop. All three were more responsive than the Martin T1K, but were not louder than the Martin. But one model, a $4000 one, was incredibly responsive. Up and down the fretboard, it took little effort, both regarding pressing down on the fretboard, as well as getting a beautiful tone to arise from the instrument. Clearly you get what you pay for here. That $4000 model was just magical. Delicately built and beautiful to touch and play.
I'm a relative neophyte when it comes to ukuleles, but clearly you get better wood boards, and better, more delicate building, culminating in a responsive, gorgeous sounding, easy to play ukulele.
I'm interested in trying the Ohana TK300G again, for reference. For sure, the Ohana is a much better looking ukulele than the Martin.
I don't have the budget to buy a $4000 ukulele. I'm more in the $500-700 range. I might keep an eye out for a used one, but I have a better sense of the qualities I'd like to find in a tenor.
And, by the way, I own a KoAloha concert, and it has a lot of the qualities I seek.