Do you intend to walk the dog, or fry it? As others have said, a TK40 on full beam is more like a car head light than a torch. 200 lumens is very bright, and even 100 is more than enough, though it's fun to have more. When I go for a run with twin lights outputting 350 lumens, cars tend to slow down to a crawl as the light is so bright, and they don't have a clue what I am.
If I had to choose one of the two you list, I would choose the TK40 because I like NiMH AA batteries. They are cheap, readily available, and very safe, and 2xAA lights are quite bright. But you are not me.
But do you want to recharge 8 AA batteries every few weeks?
You might want the TK40 for these reasons:
- Frighten anyone you meet.
- Self defence. Even 200 lumens should be enough to dazzle someone. You can also hit someone with it.
- Fun.

- Showing off.

- I nearly forgot this one. Illuminating the route ahead. 100 lumens might do, 200 is enough, more is naughty but nice, as Salman Rushdie might have said.
You could first pick up a small torch, such as an ITP A2, for general use, and to find out what sort of brightness you can get from a pocket light. After all, why buy a moon rocket to take you to the corner shop?