I would call this a classic case of YMMV (your mileage may vary).
In theory, open combs do not sweep the lather away before the blade starts to cut. Slant bar/closed comb razors are cheaper to manufacture. That's all I know about true differences.
As to my personal experience, many closed comb razors feel very rough on my skin and have a tendency to "bite" on my chin and jawline, while open combs feel and shave better. That's purely my personal experience no my own face.
I'd say that if you are curious, trying a good closed comb, a good open comb, and either a Slant or an adjustable (or both). Then you can refine what you are looking for.
For open combs, I really like my New Long Comb and will be trying a New Short Comb. I also really like my Muhle R41 2013. I really don't like my Merkur 1904 open comb.
For aggression, there are mild and aggressive razors in either category (open and closed comb).
BOTOC, GNU, LEMS, SERLover, Stirling Syndicate
New Shaver Guide - http://badgerandblade.com/vb/showthread.php/373872-My-short-and-somewhat-misleading-shaving-guide-for-those-foolish-enough-to-listen