Is the added punch and velocity over the standard 270 worth it? Does it give you a more reasonable "bigger" game rifle than the standard?
Only if you can achieve those extra FPS and Energy! I don't think it offers you anything over the standard 270 in way of making it a more capable biggame cartridge. The only thing I can see is it gives you a short action vs a long. Which some like/prefer & theory is more accurate. Ain't nothing wrong with .277 cal, it has worked for me and will continue to work for others on the likes of elk. However the WSM IMHO does nothing to raises it's level in this regard.
If I had my way, I'd just get another 7mm
You answered your own question. The 7mm mag will chuck a 150 or 160gr pill, faster, flatter and hit harder than the 270 ever will and it has better SD for the likes of Bigger Game. In my opinion if your looking for a elk/deer rifle between the 2 no contest - 7mag!!