the difference between ativan and klonopin?

My dr recently went away to care for his family overseas. Since then, ive played musical drs(not at my request, its the hospital) and this p.a decided to switch up my klonopin with ativan. Its aparently cheaper?!? anyways, the p.a suggested i take the same milligram amount i used to. SHe was kinda in and out with my appointment, didnt explain anything.
Is ativan stronger or weaker then xanax? is it fast acting? are they about the same?

: http://alcoholdrugstreatment.info/the-difference-between-ativan-and-klonopin