Feature request noted. (I know I've been taking waaaay too long to update this, I apolgize. My work schedule has been hell, and there've been more bugs that expected. I do assure everyone it is being worked on. Please bear with and understand, this is fan-created effort.
I did just get a couple of the other plugins people were looking for released though! Bit by bit, yes? )
There's two reasons higher resolution help, but they have nothing to do with compression:
a) Sculpted prim geometry is 33x33 instead of 32x32, even though the textures must be square powers of two. Aaargh. Go into wireframe mode off the debug menu and count the vertices, you'll see what I mean. I'd consider this a bug, and several people have submitted it to the JIRA already, but it keeps getting closed as "by design". (I can discuss more details of why this is so, and why I *still* think its a bug anyway, and how I would fix it if anyone cares, but honestly it is what it is, so well... work with what you got, right? Its their perogative to make the viewer however they like.)
This is also why you sometimes get a "gap" on planar mode models with smaller textures. Try putting a 32x32 on a plane, set it to planar. It *should* be perfect, but it's not, even if you individually paint each pixel in photoshop. You'll end up with a missing row of vertices.
When you use larger sizes, the gap gets filled in on scaling and you get a better match to the vertices. This same effect effectively alters the "alignment" (can't think what else to call it) between the sculpt map and the geometry.
b) The textures are only 8-bit per channel. This is what causes the stair-stepping effect. The real fix for this would be for LL to allow 32-bit per channel or floating-point textures (HDRI TIF, for example). If textures were floating point, you'd never have lumps. Scaling helps because it restores some--but not all--of the in-between values.
Scaling doesn't: a) fix compression artifacts or b) add more vertices. LL recommends 64x64 which is why it was done that way in the first place. I'm planning to add resolution control when I get the next version out.