Hey there, someone who tends to prefer "top down", I just want to take a moment to explain what I think we're talking about here, and why the distinction matters at all, so sorry if this comes off as rambling.
The "true" top down, where you literally see people's heads and shoulders, is something I'm pretty sure no one here particularily wants. So, yes, what people mostly mean with isometric as opposed to top-down here is a perspective where the subject is mainly shown at a 3/4 perspective from the above. This is what you see in the likes of Diablo and Fallout, for instance (even if technically, it's usually more a type of oblique projection).
The thing is, I don't like the 3/4 top-down isometric very much, especially not in RPGs. I associate it with SimCity and management sims; it's a cold, clinical, superior, objective, unnatural perspective which is simply not very atmospheric, even though the sprites themselves are usually very detailed and well made. It doesn't help that in most cases, the world ends up looking very flat and square; it creates a sense of perfect orderliness even when there shouldn't be one. It resembles an architectural drawing, informative but sterile, and makes all locations look and feel the same.
In comparison, what people call "top-down" - actually, a type of oblique perspective which tends to view its subjects from the front and above - has some advantages. This is what you mainly see in JRPGs and some very old WRPGs, and it actually looks pretty different. There's actually a lot of tricks you can pull with this; maps that change direction so that sometimes you go sideways with parallax scrolling, cliffs and stairs that create an illusion of height (even if it's still all on the same plane), important rooms at the end of a tunnel suddenly shifting to a more 3D perspective. It's easy to give an impression of variety in locations, even when the system itself is the same thing. In addition, character sprites take a fairly large portion of the screen, and you often see them from the front, which makes them more life-like. This is really what makes SNES JPRGs still look pretty nice; the perspective is clearly unnatural, but it's also lively and atmospheric, even when the sprites are low-res.
Now, this is the 21st century, and Wasteland is a post-apocalytpic game, so it should shoot for a more realistic visual style. Still, I'd prefer if it didn't emulate the standard isometric perspective; good atmosphere and immersion is a huge part of the appeal of a sandbox RPG, especially with a distinctive setting like post-apocalyptic. I'd prefer a little bit of both, like you see in the Infinity Engine games, which at best are kind of like "best of both worlds". Planescape: Torment in particular looks very organic, simply because the gameworld isn't actually composed of squares, and different screens have different axial orientations. A visual style similar to that could be ideal for Wasteland, with large, atmospheric, handcrafted backgrounds with good variety that aren't obviously made of block sprites.