Actually Spencer had way more value to a 3-4 team, IMO. It's not that difficult to find a guy that could match his ability as DE in a 4 man line; however, it is very difficult to find a player that can fill that role of Strong Side OLB in the Rob Ryan and Wade Phillips defenses. Finding what I call a 3 tool player is very difficult. He was good in coverage, in run defense and as a pass rusher. Normally 3-4 teams end up with a guy that is good in 2 of those 3 skills.
As the WOLB Ware had far less coverage responsibilities (about 1/3 as much as Spencer) and run defense is not as difficult on the Weak Side because that player is generally lined up far outside of the on run downs; whereas, the SOLB often was head up on the OT and often got doubled by the OT and TE.