So, I've been playing Pokémon a bit lately. In my White version, I've gotten to the point where I can breed Pokémon, which is something that I always used to enjoy in the games. Getting certain move sets could prove an interesting challenge, and I always felt that it could make desirable Pokémon for trading, though that never really came up much in the past, due to a lack of trading partners.
Part of this came from the fact that, in addition to the special egg moves, newly hatched Pokémon start with any TM that they can learn that their fathers knew when breeding. Most especially, this is of interest for TMs that only appear once in a given game. Breeding would allow me to make a Pokémon that knew that move - and really any number of them - which could be desirable to someone else who has used or has plans for that TM. Give a Pokémon 2 inherited TMs and an egg move, and it can become quite interesting.
That portion of the point seems to have been removed in the Generation V games, as TMs are now infinite-use, rendering the distinction between the two basically academic, as the only real difference is that HMs must be deleted at the move deleter's house (I assume). While there's nothing preventing me from TM-breeding as before, it seems kind of pointless, especially as I couldn't even say that I'm saving myself the cost of purchasable TMs!
This also means that TMs can be used with impunity, so there's no challenge to deciding when to use which one. :-\