The Combined version of Continental knitting evens out your stockinette because the yarn travels a shorter distance to make a purl. Your purls thus become tighter and more like the tension of your knit stitches.
It's also a much easier way to purl -- less wrist twisting.
I'm not a "pure" Combined knitter: I use it for stockinette and for some rib stitches. I use regular Continental for garter stitch (because no purling is involved) and fancy stitches such as lace (because I'm too lazy to "translate" the increases and decreases).
It's worth the sort learning curve to get beautiful stockinette. Go here: http://www.modeknit.com/knit.html
Or, if you have Mary Thomas's Knitting Book (and IMHO, everyone should), look for "Eastern Uncrossed Knitting."