Well, between the SnG, Sebbie, and XM-18, here are my thoughts:
My SnG is a great knife, and after thinning out the profile a little bit, it's a superb slicer. I carried it quite a bit until it delveloped some sloppiness in the lockup. (Still need to sent it to the spa). After carrying a Sebbie, the SnG also feels a little big for carry. Due to the lockup issue and heftiness of the SnG, it usually gets left behind for the Sebenza.
The XM-18 is a fantasitic knife, no doubt about it. The thing about the XM (for me) is that it's even heavier than the SnG, making pocket carry even less desireable. The blade is also a little thick for my taste, and I found that after carrying it and handling it for a while, the handle shape was a turn off for me. I have a habit of flipping and manipulating blades around, and I found the ice pick grip to be most uncomfortable.
The Sebenza will forever be a mainstay for me. All hype and fanboys aside, I feel the Sebenza to be one of the most comfortable knives I've had the pleasure to own. As many times as I've opened and closed it, the lockup still feels the same now as it did when it was brand new. I have a small classic, and for pocket carry, it's perfect. Thin profile and lighter than the others. It doesn't feel like it's in the way when I reach in my pocket like the others. I use it almost exclusively every day, and it barely looks worn.
The only issues I have with the Sebenza are these: I was worried the thin blade wouldn't be that strong for EDC and would be prone to chipping. So far to say, I haven't had any problems with that. The only other gripe is the pocket clip. I'm a fan of the older style. I find the newer style with the bump in the middle eats my pockets up rather quickly.
I try not to choose favorites, and I like trying out different knives for edc, but the one that constantly finds it way into my pocket is the Sebbie. I'm still looking for someone to unseat it and hoping the Busse folder will be the one to do it. As much as I like the Rat Trap, I hope Busse scales the folder down in size a little. Large knives are great, but are harder for a lot of people to carry and justify in the workplace. I find the size of the small sebenza to be just about the perfect size for an EDC blade.
-Dan