The ballistic advantage between a .270win and a .30-06 is largely academic. We hear about it all of the time, and the difference IS obvious on paper, but when it comes to the hunting field, it really doesn't matter at any reasonable range where either are truly effective on game (500-600yrds).
With similar bullet weights, the .270win runs a higher BC and higher SD, but it loses a bit of speed, so at 500yrds, the difference seen on paper really doesn't make much difference in the field. For my loads with 150grn NBT's in both end up about 100fps faster in the .30-06 than the .270, the SD's .226 vs. .279, respectively, and BC's .435 and .496 respectively. Seems like a big difference, no? But at 500yrds, I only have ONE INCH of difference in trajectory, and within about 30fps, favoring the .270win. IN THEORY - I get a little better penetration with the higher SD .270win, but get a little harder hit from the fatter 30cal, but I can honestly say, I've had a whitetail write me a letter of complaint with either of them.
When you talk about "ideal weight for bore" bullets between the two, say the 130/140's for the .270win and the 165/180's for the .30-06, then you start talking about less of a difference in BC and SD. I also shoot the .277" 130 and .308" 165 Hornady Interbonds, with BC's of .460 and .447 respectively, and SD's of .242 and .248, again, respectively. In my loads with these bullets, the smaller .270win is running about 200fps faster than the .30-06. At 500yrds, I only see about 7-8" difference between the two, which SEEMS LIKE a lot, until you recall, that's only ~1.5MOA difference between the two. Dialing 34 clicks instead of 29 clicks really isn't a big deal, and alternatively, if you're HOLDING instead of dialing, if you can accurately hold 38", then you can equally accurately hold 46" (200yrd zero).
Anything longer than 500-600yrds (maybe stretched to 750yrds if I'm honest), I tend to throw a magnum round with a heavier bullet, stepping up an entire class (or two) in performance.