Sierra came out with the cannelure so they could be compliant with spec changes to the Mk 262 ammo. They had the contract, lost it to Nosler when the spec changed to w/cannelure, now came out with their cannelure option and won the contract back.
If you wanna be "spec", get the cannelure. I've shot thousands upon thousands of 77s without cannelure no crimp and never have had problems with bullets moving. Started shooting them when they came out in like '97. Slung oh 2k+ of them down range in 2008 alone, all precision shooting in an AR, no blasting.
This stuff is in Mod 1 boxes but loaded with Mod 0 bullets.