If you are trying to say that 91 Eagles defense was as good as the 85 Bears defense, you're insane.
Sorry it had to be that team, but yeah, they were, by most objective measures... short of playoff success :) .
Statistically only the 2002 Bucs had a better pass defense, and only the 2000 Ravens had a better run defense.
The 1985 Bears in their entirety were the better team by far, but their defense had the benefit of a stud-filled offense too.
Three of the 91 Eagles starting defensive line were All-Pro. I just thank god their offense was hot garbage with Randall Cunningham out for the year game 1, otherwise they probably beat Washington who had nearly as good a defense but a far better offense. Our emerging Cowboys also barely beat that team late in the year... after they crushed us 24-0 to start out.
I take 4 of the 5 pro-bowlers from that Eagles D... Eric Allen, Seth Joyner, Jerome Brown, Clyde Simmons, and Reggie White over the 85 Bears' 5 pro-bowlers Mike Singletary, Dave Duerson, Otis Wilson, Dan Hampton, and Richard Dent. The best Bear was Singletary, and he can't hold a candle to White. Not on his best day.
I'd take Singletary over Joyner, though, because of his leadership.
Eagles allowed an insane 3.9 yards per play and the Bears 4.4. Bears forced 54 turnovers, Eagles 48. Just imagine if the Eagles had a QB, for a while they were on their 3rd string guy!