I shoot with the M240 and most of my work is in the landscape arena. Like others have pointed out, if you're used to shooting 8x10 and 4x5, ANY smaller format is going to be disappointing. I think the largest difference you'd see is gradations in areas like the sky, but yes, there would definitely be less resolution when compared to a 24mp 24x36 sensor. Honestly, you wouldn't expect 135 or 645 film to be comparable either, would you?
That being said, the type of sensor can make a difference as well. My old M9 and M8 showed more acutance with the same lenses than my current M240, but with the M240 has a broader dynamic range which is very useful, so there's always trade-offs. Lately I've been shooting more with a Hasselblad and 22mp P25 digital back, and the Hasselblad, despite having a lower pixel density and less resolution than the M240, shows a lot more acutance and better gradations but can also require more post work to make "pop" and has a narrower dynamic range.
Anyway, the point being that more pixels may not be the answer you're looking for but the only way to find out would be to borrow or rent different gear and see what works for you. I would recommend checking out a couple of the more reasonably priced Medium Format cameras and see if anything in that realm works for you, but keep in mind that nothing has been invented yet that can replace 8x10!