The reason TMSR is appealing is that U-233 is hard to use for weapons purposes because it produces a lot of gamma radiation, which makes it hard to work with. There is also the claim that TMSRs are much safer designs than is possible with Uranium. It's possible that if TMSRs were mass produced that we could see them installed in many countries where we don't want to see Uranium or Plutonium reactors for proliferation reasons.
With a Uranium-based reactor you need a) a source of enriched Uranium (see proliferation risks), b) inspectors to check that you're not post-processing fuel rods to extract Plutonium.
With Thorium if the operator country wants to extract the U-233 you think "maybe let them, they won't like it".
With classic pwr rods can't be used for weapons because of parasitic isotopes. At best you need to run the reactor in a specific way that would trigger global attention looking at power fluctuations. And still it'll not be easy afterwards.
You can buy enriched uranium from others.
With th- I'm not sure but don't you need enriched material anyway to kickstart it?
