Honestly, I think that Komugi is better watched after SoulTaker, for two reasons: it's the better show of the two, and it's absolutely hilarious to see all the grim and serious characters from SoulTaker in an entirely different and goofy setting. I got so much more out of Komugi after having watched SoulTaker first.
I will say that SoulTaker isn't wholly bad, but it's also a really weird show. It has a borderline nonsensical plot that's kind of a bitch to follow yet simplistic at the same time, but the visuals are pretty striking and it's got some fun battle scenes. As a friend of mine said, it's the exact sort of show that teenage me would have thought was the coolest shit ever if I caught an episode late at night. Not my least favorite show I've ever watched, but I have no desire to rewatch it. At least it's short, so you can power through it in a day.
Fun fact: SoulTaker was dubbed by Ocean, but ADV got the license to dub Komugi. Knowing that people liked the Ocean dub's actors, they managed to get all of them (except one I think) for the Komugi dub as well. Really is a shame ADV went under and we're left with garbage Funi/CR dubs for nearly everything.