Oh, sorry I misread that.
I think as a defender that it's tough to play spread offenses simply because it's difficult to match up man for man with the talent at WR and TE in good spread offenses. If you add a talented back, it's super hard because you have to spread the defense out to account for the WR.
Any Spread or Air Raid playbook would fall into this category.
You can play man against an offense like that and try to negate the WR threat with press coverage, but the offense is likely to win at least one matchup and you're left in a lurch in a man situation if that happens.
You're also in a bad position in a man defense versus a good TE, who will beat the LB frequently. If you combat that by putting a DB on him, you're removing another LB from the defense, making the threat of the run a serious one.
Now if you play zone vs. a spread offense, you have different problems. You can play cover 2 soft with the safeties set out, but your live opponent will see this after a bit and kill you in the seams. You can go cover three but will concede shorter passes over the middle and longer passes in the seam.
There are tons of plays in the spread that are custom designed to flood any zone you like on the field. A smart offensive player will pick up on your zone preferences and choose flood plays to that zone.
In defending the pro style offense, I'm less worried because I have to account for less talent at the WR position and can play the run fairly easily with manual DL or LB play. Taking the run away from a pro style offense murders it, and since I don't have much trouble with that offense I think it's not as hard to defend.
Just my .02. Hope I got the question right this time. If not, I'll put on the dunce cap.