Have you made a decision yet? I know your original question was asked a couple weeks ago but I thought I would weigh in.
I owned a 2001 A4, I bought it in 2006 with about 45k on it. It was a terrific car, I loved the heck out of it. It was on the smaller side but it looked great, it had 18 inch sport rims and it was a MT. However, it was pretty needy car. I had to get a new timing belt at 60 k. Lucky for me a friend of mine fixed some of the minor issues pretty cheaply. There were lots of little issues though and the parts are super expensive. It seemed like once per month the check engine light came on. There was always something wrong with it. I had to trade it in for a 2010 Forester XT before it was paid off because I couldn't afford the repairs any longer. I would definitely choose the Legacy over the A4 unless you can find the A4 with about 20,000 miles on it.
As for the IS 250, this was kind of my dream car for awhile when I had to get rid of my Audi. They look great and have AWD. However, like many others have said theyre really small. They also dont handle that well for a supposed sport sedan, nor do they accelerate quickly. My next car will probably be a 3.6 legacy and I feel ok eliminating an IS250 from consideration.
How did you like the test drive?