They are great in a 46 speed - gets more of their fast talent on the field. A 4-3 & 3-4 puts too many secondary players on the field - bowen, hatcher, v. butler, etc. and leaves some of the better secondary on the bench. While the secondary stunk in real life, they're great for madden 'cause they have great speed and pretty good man.
Newman is 97 speed, McCann is 96 speed, Jenkins is 93, Scandrick 92, plus AA is 91.
With 4-6 speed, you can get all of them, plus olshansky/ratliff at DT, spencer/ware at ends, lee at LB and Ball/McCray at safeties. Lots of speed to get to the ball and if you play 2 man under, then most teams don't have enough receivers with the speed to get away from the coverage.
You can also put v. butler & b. williams or the DE's as #2 slots for ware/spencer so when they do go out for a breather, there is a reasonable sub coming in for them.