here's a quick run down on the trim levels:
2.0S - Dual Carbed SOHC engine, no power options (windows, mirrors ect.)
2.0Si - Fuel inj DOHC engine, 88-89 has all power options. 90-91 power stuff was optional at time of purchase, some will have em, some won't. (4ws available in 88-89)
Si - Fuel inj DOHC 2.1l (90-91 only) all power options. (4ws or ALB available)
the differences between 88-89 and 90-91, other than the Si being availble, are mostly cosmetic differences, such as tail lights, front bumper, gauge cluster...

Bad things about 4ws? there's nothing bad about it. The 3rd gen 4ws is completly mechanical, there is nothing that can go wrong with it.