To me, they're very different styles. Tactical strategy has a lot more depth to the battles, for sure, but they also take a lot longer (unless you're doing something like Ogre Battle: MOBQ, which is more like an RTS with an unconventional battle system than an RPG). In a game with random encounters, you're there for the story, with the random battles being just part of the challenge along the way. I'd say that's true of games with map-visible encounters too like Earthbound or Chrono Trigger (or with radar, like 7th Saga). With a tactical strategy game (Shining Force, FF Tactics, etc), it's *all* about the battles. The story can be done very well, but it's very often an excuse for the battles, which are the centerpiece of the game.
In both cases, the battle mechanics are the central gameplay elements, but it's presented in a different sort of way, and they're definitely not interchangeable. Try to imagine Final Fantasy 7 with grid-based tactical battles or Shining Force with FF7-style menu-driven random battles, for example.