A friend and me were chrono-ing loads from my 270 Win and his 7mm RM. Both shooting 150g bullets. He'd been bragging for years how much harder the Big 7 hit than the 270.
Since then he's worked up some proper handloads and now has that Big 7 shooting closer to potential. And now it craps all over the 270.
My rule of thumb is the 7RM will shoot the same weight bullets about 200 to 250fps faster, or for the same speeds the 7 will shoot bullets about 20g heavier.
The 7 is noticeably more gun, even though the 270 Win is my favourite.
