Which Defense/ST to add, steady Colts or streaky Seahawks?

[SonOF]

I currently have the Bears and Bills defense/special teams units on my roster. I had the Bills simply as a bye-week replacement (and because of their matchup with the Browns) and am ready to drop them. I plan on keeping the Bears, but don't think they are good enough to start each week regardless of matchup. The teams I am considering picking up that are on the waiver wire in my league are the COLTS, CHARGERS, and SEAHAWKS.

The Colts have been a quality unit, not having any monster games, but putting up steady points each week. The Seahawks have been quite the opposite, having very big weeks, and very poor weeks. The Chargers haven't been great, but I think they have a lot of big-play potential if they get it together..

Who do you think is the better pickup in the long run? If I pick up the 'Hawks, I will start them this week over the Bears (who play @ Atlanta), when they play at home vs Arizona. If I pick up the Colts, I will sit them this week on their bye, then start them next week for a great matchup vs the Rams.

What do you suggest? Thanks in advance...

[SonOF]

bump..help?