If I were to change to 1:1.5 or to hexes I'd take the time to work out alternate shaped for blasts and busts such that the area remains the same, and work out alternate movement speeds such that the potential number of sqaures reached remains roughly same.
I like "realism", but I don't feel this particular enhancement is really worth the bother, however. Both counting methods are inaccurate, and the discrete distinction between difficult terrain and non-difficult terrain is quite inaccurate, and the similarity in speed between characters is a little off, and the relative irrelevance of heavy armor is a bit off...
It's unfortunate, and if you can think of a better system at no cost to complexity, that'd be great. Otherwise, it's a trade-off of believability and consistency vs. simplicity. If you want to change the details of that trade-off, you're automatically losing a lot - to be fair, you'd need to rebalance large sections of the game.
For example, even if you adjust speeds and areas such that they cover the same number of (possible) squares, you'll still need to deal will pulls and pushes - they'll now permit many more odd paths if you use the same rules. You'll need to address charging, which will be much less flexible than it currently is. I bet there are more things, and then you'll be left with indirect consequences - what do you do to classes that do a lot of movement, or have a lot of area effects, or that do a lot of charging, or pushing or pulling if each of these basic effects has been rebalanced?
So I think it's doable, but it's a serious undertaking if you want to change the distance counting measure. If you change the measure because it's "more accurate" but then fail to look at all the consequences and potentially adjust those, you're buying fake accuracy with a dash of unbalancing game breakage for your time investment...
Having said that, if you do systematically look at the consequences, I'd be very curious to see the analysis posted. Good gaming, anyhow!