I do not have an E36 but I do have a pretty decent knowledge in suspension set ups for BMW's in general. On my E39 I had a tough decision to make between coil-overs and a run of the mill (so to speak) sport/race strut lowering spring package.
Coilovers: They are fantastic in terms of ride height adjustability, dampening adjustability, and overall adjustability. However, some are a real PITA to setup properly and can take some time to reach a compromise between street driveability/race car handling. You're also going to want adjustable caster/camber arms, camber plates, etc which will also factor into the already high cost of some coilover systems.
Sport struts/lowering springs: Headache free and require minimal additional modification to setup (caster/camber plates, adjustable control arms, etc.) Ride height will be as is for the most part which is a good/bad things depending on what you want. Great option for a street car but a compromise if you ever plan to track the car. Relatively cheaper to do than a coilover system and you do not need to worry about constantly adjusting ride height and dampening which definitely makes life easier.
I inevitability decided to go with sport struts/shocks and lowering springs at first. I bought a Bilstein/H&R package from Turner Motorsport and it made a huge difference in handling right away. However, I also had to replace the factory strut bearings and rear shock mounts as they were showing signs of wear and tear. I completed that first suspension mod in June of 2008. This summer I kicked it up a little by adding Powerflex control arm and swaybar bushings to my front/rear suspension. I needed to replace my factory UCA's and LCA's and decided to give Powerflex bushings a shot and I could easily tell it firmed up the front suspension a little bit. During this time I changed my rear subframe bushings (which looked to be in good shape) with OE bushings and the rear ride definitely improved drastically. I also added a front strut brace which tied things together nicely and I'm hoping by spring of this year to install Eibach sway bars both front and rear.
Currently my setup is as follows...
Front:
Bilstein Sport struts
H&R lowering springs -1.3"
OE UCA+LCA's
Powerflex control arm and sway bar bushings
HD strut bearings
Racing Dynamics strut brace
Rear:
Bilstein Sport shocks
H&R lowering springs -.75"
HD shock mounts
Powerflex sway bar bushings
OE subframe bushings
I like the setup overall but in some ways I wish I had coilovers...
I also went from 17x8 ASA AR1 wheels all around with 235/45 rubber to 18x8.5" front and 18x9.5" rear with 245/40 front and 265/35 rubber rear. That made a huge ride difference and handling difference in two ways.
1) I feel everything on the road
2) Wider tires have given me more grip and the lower profile tends to flex less
Those are just my observations though...