I own a G26 and a SW99c ...
When it comes to overall dimensions I find them very similar.
Both are excellent small 9mm pistols.
I find the grip profile and angle of the SW99c to be preferable, all things considered, and the smaller grip insert makes the 99/990L compact pretty small when it comes to grip 'feel', but that's a totally subjective consideration.
While I prefer the TDA of the SW99c I own, I've used a few of the 990L QA-type compacts. In my personal experience and opinion they offer a smoother trigger stroke than the Glock, but not really enough for me to get too excited one way or the other. I find it interesting that the Walther QA action 'feels' lighter than the standard Glock, in some respects, even though it's not. There's that perception issue at work.
Now, after having fired several thousand rounds through both models, I can offer that while I consider the G26 to be an inherently accurate little 9mm pistol, I've found I can consistently achieve slightly better practical accuracy with the SW99c, but then you have to remember that I favor TDA action, and mine has the TDA action instead of the QA-type action. I might feel otherwise if mine was the QA-type 990L ... Dunno.
If at all possible, it would probably help you answer the question for yourself if you could fine a range where you could rent both models and send a few hundred rounds downrange over the course of a few different days. Some folks express surprise that their perception of how a handgun might 'feel' under live-fire may change from one range session to another.
I think both are quality examples offered by the different manufacturers ... and I have no plans to part with either of mine.
