Zach is a MLB and would be around the ball more often. In that case we should compare LondonFletcher to Zach Thomas, but when we compare Takeo Spikes you are looking at a guy who is expected to play pass coverages and defend the run from the OLB position.
I'm not sure if this counts, but Takeo had 5 INT's last year, 4 Forced Fumbles, and 3 sacks. I have to assume those are some serious play making stats.
Zach had more tackles, but any MLB should have more tackles then an OLB.