Well, SOAD is closer to pure metal than Drowning Pool, let's just leave it at that. Some of SOAD's riffs do remind you of original thrash - but that's it.. The Serj's chaotic voice drives people like AllWithinMonster away a little - but that's their style.. Some people like it, some don't.
Drowning Pool are (were?) a typical Nu-Metal band. That didn't automatically make them bad - no, but I wasn't that fond of them, to be honest.. They were REALLY overhyped after Ozzfest '01 which I attended - people just jumped on their bandwagon when there wasn't anything that groundbreaking about 'em at all.
I do like SOAD, though. Possibly my favorite Nu-Metal act..
As far as Disturbed singer goes - I don't like his monkey growls - but when he sings cleanly (and I saw him do that live at the same Ozzfest) - he
can actually do it well (has this Middle Eastern vibe - I'm not joking).. He IS Disturbed - the band is nothing without him - love him or hate him... Their latest album was very commercialized and lost all its metal influences - became just rockish.. So it wasn't for everyone
. But it had some bright spots on it..