Looking for advice on buying my first track bike

Hi r/trackdays,​My Ninja 400 got stolen yesterday and I've decided to just get a track bike and stop riding on the streets altogether.I have some experience driving cars on tracks but when it comes to riding (well, driving as well), I've got a lot to learn (still hanging out in beginner groups)​I'm thinking about getting a 600 because most people in my events ride them. I was the only one riding a sub-600 in the last few events and I could hang with a few 600s in the corners.I would go for a more exotic European bike if money were no objects but the sensible part of my brain tells me to stay with the big 4.​I live in an apartment (that's how my bike got stolen) and I plan on storing this track bike at a friend's garage. Working on the bike is going to be problematic because of this and I plan to have a shop to perform most of the work.My questions: does it matter which one from the big 4 I get? How different are they anyway (looks aside)? Roughly what year should I be looking for? I'm willing to spend a few more grands upfront to save a few trips to the shop.​Thanks in advance. via /r/Trackdays https://www.reddit.com/r/Trackdays/comments/cgstak/looking_for_advice_on_buying_my_first_track_bike/?utm_source=ifttt