JQuery :: Improving Efficiency Of DOM Injection?

I've implemented jQuery within a web application where a very large number of DOM elements, comments in this case, are injected post-load by a 'Show all' button. Returned via JSON is a HTML string of <li> elements, to be injected into a pre-existing <ul> element. I'm looking to make this more efficient, as reading various sites I've been led to believe that wrapping new elements in a parent wrapper node before injecting would yield the best speed. Here, however, I'm injecting into an <ul> element that already has elements in, so can't wrap it.

What's the most efficient way of tackling this?
a) Wrap them in an element, inject, then unwrap and move into the target?
b) Clone the existing <ul>, add the elements in-memory and then replace in the DOM with the consolidated version