the I6 is good for about a second and a half difference in zero to 60 compared to the 318ti. What does not tell you is that the aggressive gearing in the Ti requires a shift to third at roughly 50mph if you hit the redline fuel cutoff in second. Up until that point, the Ti is not that far behind the larger engined 325i.
It all comes down to weight. the i6 engined cars all weighed about 500 (or more) than the i4 ti. The sedan and coupe' I4s all weight a few hundred pounds more than the Ti.
To group the cars from best to last... M3>328>325>318ti>323>318i. You will find the ti is slightly "downmarket" in the interior. It's dash is similar (but not the same as, though most people will swear it is the same) to the e30. Funny enough, the e46 also went to a "pod" in front of the driver instead of the e36's sweeping dash. The door panels are cheaper (and similar to the e30) and a lot of the niceties of the sedan and coupe' are missing. You cannot get automatic Climate control, power opening rear side windows, 7,11,or 18 button On Board Computers (we get a 2 button) and the ti never got a fuel economy gage (seems silly for the most economical of the E36 range)
You will find a lot of the same problems. Falling down headliners, falling off door cards, failing power windows, plastic radiators, thermostate housings, and plastic in the waterpump. Not to mention the soft BMW rubber bushings that all fall apart by 100,000 miles.
An interesting note of what you will NOT find that is a good thing. the ti was the ONLY e36 fitted with electric fans instead of the viscous coupling at the waterpump. Means you NEVER hear of a fan disintergrating and taking out the radiator (though to be honest, all the fans disintergrating are probably due to worn out engine mounts allowing the fan to hit the shroud or the waterpump going)
The rear suspension is more "Lively" as said above. I do not see the big issue with it. in 40,000 miles of spirited driving, it has only ONCE caught me out, and that was when I first got the car and all the bushings were bad and the shocks/struts blown.
Over all the Ti is a "cult car" you either get it or you don't. It is one of the rarest e36 models in the US (aside from the m roadster and coupe') that in my opinion combines the very best of the e30 and e36 into one smaller (9 inches shorter) car. As a bonus you get a hatch that can swallow cubic yards of stuff without complaint.