Sheet zim is less time consuming...but...it requires some putty in the right places to eliminate gaps (i.e. Panther mantlet, etc.). I've got an "A" on the bench now and I am using Eduard aftermarket zim. I've also used putty and done it all myself, but maintaining the correct thickness is time consuming. You can make sheet zim appear chipped, and it really looks good. The thing I like about sheets is maintaining scale.
Steve