It's actually not ```$.get``` vs ```$.getJSON``` but rather the inclusion of ```?callback=?```. This triggers the ```dataType: "jsonp"``` which wraps the data in a callback on the server, and then includes a script element in the page, which is a) unnecessary in this case, and b) is significantly slower.

I put together a quick test at http://jsperf.com/get-vs-getjson-vs-ajax which shows the performance hit that ```dataType: "jsonp"``` takes.