I don't have a Kobra, but I have had 3 Sirupati's over the years and still have 2 of them. My 20" 24oz Sirupati is a Fast blade akin to a short sword. I've cleared trails, weed wacked the yard, cut up food and killed boxes with it.
My 15" Sirupati sits next to my desk as a Bump in the night knife. It also goes with me on trips when I want to travel light and not draw attention to the fact that I have a "big" knife on me. The "Little" Sirupati hides well between my webbed belt and butt pack or lashed to the side of a larger pack. I've done a little brush and wood work with the 15" and it does well. Even so, my 20" Sirupati is my favorite and most used Khukri.
Hopefully someone that has both in the same lengths will be along to give you a good idea of their differences. Since I don't have experience with both, All I can recommend is a 18" to 22" Sirupati thats light and fast. Just from reading other peoples posts I would lean towards a Kobra for just M/A stuff and a Surupati for M/A and field work. Hope I haven't muddied the waters to bad. :foot: