Lexus ES350 (2007) vs Infiniti G35 (2005) vs BMW 3-Series (2005)

[PainCakes]

Alright, so I'm currently a college student (4th year) and drive a 1994 Subaru Legacy. I'm expecting to make some money over the next year (getting a part time job) and expect to have around 12-13k saved up by that time. I intend to go to medical school after graduating and thought that I would like to buy something nice for myself once I graduate. My parents were kind enough to pay my way through college, meaning no student debt. The 12-13k therefore will be spending money for myself (I have some money saved and put away as well).

I am personally looking for a luxury / sporty car, and the Infiniti G35 as well as the BMW have caught my eye as being cars that are within my budget as well as good cars overall. (2005 models respectively).

That said, my mom is planning on buying a new car and has said that she is willing to sell her 2007 Lexus ES350 to me for around 10k. It is fully loaded with navigation, only has about 45k miles on it and is well taken care of. My only complaint is that it is not terribly fun to drive. I've driven it many times and while it is surely better than my current car, it wouldn't be my first choice.

My dilemma here is that while the ES350 isn't quite what I want relative to the Infiniti and BMW, the deal she is giving me is one that I feel may be too good to pass up. My friend suggested that I just sell it after she sells it to me, but given the fact that she's selling it so cheap to me because I am her son, I feel it would be kind of rude for me to turn around and sell it for a profit right after. Therefore, I wouldn't feel to comfortable doing that.

I'm completely on the fence on this and have a few questions:

1. Which would you go for in my position?
2. What are your opinions on the Infiniti and the BMW? Are there any other recommendations within my price range that you guys have?
3. I hear that BMW maintenance costs are significantly higher Lexus and Infiniti. If this is true, how much more would it likely cost me? Is it significant?

I'm hoping that you guys can educate me and help me come to a decision. Thanks!