It most of all depends on your personnal taste.
My personnal no-sale pointer for the M-30 was the lack of regulation:
Look at some regulation graphs for both these lights: the M-30 doesn't seem to have any, which means the second you turn it on, it starts to dim.
On the other hand the TK30 has excellent regulation: it will have the same output until the batteries are too low and then just go to the next lower level until the batteries are too weak for that level again (at this point not very very long, though), and so on.
Then ask yourself which of these two aspects do you prefer. I haven't found any beam shots that compare the two diretly, so if you don't have a light that strong yet, you'll probably like how bright the thing is when you receive it, no matter which one you choose.
As an extra, I just got a Jetbeam M1X (exellent regulation as well) and already have a TK40 (which is the same as a TK30 except for battery type and apparently user interface) and I can say that there is no visible difference in intensity and spot size, but the user interface is different (twist the head for high and loosen the head for user-defined mode on the M1X) The M1X interface is more straightforward (can't talk about the M-30 since I don't have one) and I like it a lot, but for those who like to go through all the modes on a regular basis, the Fenix interface is better suited for that... just thought I'd give you a heads up on a very similar light