Long answer: yes
Short answer: yes
lol...just kidding. Well, not really.
Think of it in terms of an N/A motor. Do you get more top end power out of a 270 than a 260? Yes, about 8whp on a dyno. Not to mention a whole lot more torque under the curve. Not much, but its NA, and thats on a stock head. But add boost....Booya.
Which 260, btw? The asymmetrical 260/256 or the symmetrical 260? The symmetrical 260 has the same 0* overlap @ 50thou valve lift as the 270.