I have both, a Spector Euro LX-4 and a Wal MK1 4 String. I also love Tool and like PT...
Tool bass sound can only truly be achieved by using a Wal. The sound it produces is very unique, mid heavy and has a truly awesome voice. But...
A pick and a sansamp can bring you in that direction quite good. Some basses do it better than others, most notably twin humbucker active basses like Musicman Bongos, but even my squier jazz bass can get a nice toolish sound with the sansamp and a pick.
The Spector has an awesome sound in itself, but i don't think it is suited for a Tool sound. The Spector has a hifi sound with huge bottom and crisp highs, yeah and "THAT Spector sound". It is a unique beast all itself.
To conclude: for me the spector sounds better played with fingers, has a punchy and crisp sound but sounds just too thin and precise with a pick. I would need pedals and quite some EQing to get it anywhere near Tool territory.
The Wal sounds completely awesome played with a pick and instantly sounds like Tool with no other components needed. It sounds a bit dull played with fingers imo though.
All that said, i do prefer the Spector. I don't know how much longer i will hold on to the Wal. It just sits in the mix so perfectly while you need to tailor the mix quite a bit to make the Wal shine. I played it with lots of presence in a 3-piece band, and it totally excels in that role. Right now i play in a Band with two guitars and some electronic/keys/synth, and the Wal is just too much.
Edit: on Youtube, a guy called Remi Zik plays Tool songs with a custom build bass and some older vids with a EBMM Sterling. He nails the sound quite good, main recipe: pick, sansamp, awesome playing skills.
Then there is "toolbassplayer", who basically has the exact same rig as Justin Chancellor. Both are worth looking at
