IMO get the lower mileage manual if you can find it! but have a drive first (if you haven't already) to make sure you do like it.
Firstly, why is it people think j-spec insurance is like twice as much, if you shop around it doesn't need to cost _any_ more at all, so there is no need to worry about that.
Secondly, the auto is slower not quicker, lets not have that debate again lol. Of course you need to be able to drive the manual. Put a novice in the car and they would fair better in the auto every time. Put a decent driver behind the wheel of a manual and he is going to make best use of the 6 gears rather than 4, the better control and the lower power losses...
If you want a daily driver and you do a lot of town driving, I can see why an auto would be appealing though! horses for courses really, depends on what you want out of the car and what floats your boat so to speak. I've never been an auto fan and as good as the supra auto box may be, thats still not enough to convince me 1 bit.