I made up my mind about the very same thing just a couple of weeks ago as well. I finally decided to go for a used 75-300 III USM
without the IS
. The money I saved goes into my funding for an L lens.
For now I'm pretty satisfied with the lens. Of course the IS
performs a bit better especially in low light conditions, so if you are looking for a lens to guide you along for many years, go with the IS
. If you just want a lens to get you started take the one without IS
, and save the money since you're likely gonna upgrade to an L lens anyways sooner or later.