Honestly it depends, Currently it would be easier for us to field a 4-3 from our current roster IMO, but also I could see some players like Bresee on our roster benefitting from a switch to a 3-4.
It's a lot easier to think less in 3-4 or 4-3 and more in base vs disguise. Perfect example is the Rams who are technically a 4-3 but disguise their rush and coverage very well.
Base defenses where the same 4 rush often and the same 3 linebackers often drop back into coverage is becoming obsolete. Disguises and having the personal to disguise the rush and the coverage have become prime defenses.
I know its a touchy subject. But Baun for the Eagles is a perfect example. Is he rushing? Is he spying? Is he dropping back in coverage? What's going on with him? It means your QB has to take a second to watch key personal and what they do and know what route that opens up, which means they hold the ball a second longer.
Theres just not a base defense that excels anymore in this league.