RE: Slug accuracy?? which is better??
Another vote for the Federals.
I have done the cornicoupia of slugs thing and when all is said and done the federals grouped the best out of my rig (Browning BPS + Hastings fully rifled barrel). They kick like a mule (not as bad as the buckhammers or the old Brenekie Rotweils) but significant.
At the range they will make a nice cloverleaf at 50 and about a 2 1/2" group at 100 (shooting from a sled).