Well, one of the biggest differences between Aikido and kendo is that in kendo they tend to have a rather unstable kamae compared to aikido, because they have no need in moving sideways in kendo when they have this big protective armour thing called "bogu".
In Aikido we always lower our hips and stand in a stable hanmi because we have to move in different directions. In aikido we don't use (or have the access) to an protective armor which prevents us from full-contact training like in kendo. Another thing that differs from kendo is that we tend to not
have our backs straight. (I don't really see the point in doing that, but it's just a thing we do).
I remember when we had an "Aikikendo"-day in our club when we did some awaze-techniques in full contact training in kendo armour. Suddenly, the aikido-kamae with "lower your hips" thing became almost unreasonable. Then we did some jigeiko, and then again the aikido-kamae was useless, and so did the "bend your back forward-thing" too.
So if an aikidoka met an kendoka in a swordfight, I think the aikidoka would be chanceless (unless he disarmed the kendoka).