I'm a 3-3-5 guy. Used to be a 3-4 guy.
It's really not that much different though.
My Sam Linebacker is now just a Nickel/Linebacker hybrid instead of a true big bodied LB.
You want somebody who's in the range of 6'1" 190+ who can run, blitz, cover and tackle. This provides you with the flexibility that a true Nickel doesn't. (a true Nickel is too light to do certain things)
A big Nickel/hybrid allows you to get in and out of different fonts easier. He can cover + set the edge versus Tight End sets + blitz...and if you try to run bubbles at him he can obliterate most WR's who try to block him.
The defender on the opposite side of him in the 3-3-5 is our "Rush" Linebacker. He's a hybrid LB/DE type. Someone who's strong enough to hold the edge yet athletic enough to rush the passer and occasionally drop into coverage. And truthfully he doesn't have to be THAT athletic because when he DOES drop its generally only to the flats.
This allows you to utilize the element of surprise by occasionally bringing pressure from the field while dropping the Rush.
My Rush is a 6'1" 225lb kid who has numerous sacks and a pick-6 during one of those surprise drops.
These 2 positions...along with the Nose...are the recipe that makes this defense work.
The amount of fronts and blitzes that we're able to run during the course of a game is crazy...on top of all the slanting/ stunting we can do.
We'll be in "Bear" front one play and then 4-2-5 stuff on the next... while barely changing personnel.
We've only given up a total of 416 yards rushing on the entire season at 1.7 YPC...and that includes a schedule with Milton GA, Coconut Creek, STA and Heritage. (only gave up 3.7 YPC in those 4 games combined)
IMO if you're lining-up in a traditional 4- front all game every game, you're dead meat at some point