TBH I only test drove (accompanied by salesmen!!) one 313 and one 326 so am far from an expert on those models and certainly can't comment on their high speed cornering abilities.
One of them, I can't remember which, had pretty poor throttle lag which I didn't like - but could have probably put up with - and was just about to push the button when I stumbled on the 340 (plus) version which was coming soon.
This was my first (probably last) brand new car so I wanted to get it right. It was about £4 or 5K more expensive than a 326 but has 340bhp and an extra 50NM of torque which was enough to make me (shallow or what
)want it, the diff (witchcraft), quilted leather and other interior add ons were a bonus.
I ordered one before they were available to test drive and have not been disappointed, throttle response is instant, torque shove is addictive, handling for an SUV is incredible, it's decent on fuel and great for towing as well.
Downsides are the brakes, headlights and tech, MMI looked dated even when new - but that doesn't bother me. I've already upgraded the bulbs and will change the pads for the ones John recommended soon.
Admittedly I was slightly miffed when just after I got mine they brought out the plus SE runout model, that's got every extra as standard and with discount could be had brand new for about £47K !
No matter what one you go for you'll love it, the bitdi is a fantastic engine.