The less-exalted eta-engine E30 is fun; it's cheaper than the 'is' version, too.
Pros: Relatively cheap to purchase. Tell your wife or gf: "It's cheap. What's the harm? Come on, honey...."
Very ruggedly built. The M20 is a very tough engine in either the 'i' or 'eta' variants. Safer than the 2002 in a crash.
Much less prone to rust than the 2002.
Parts availability is very good. Prices are not too bad either.
More power/torque than the 2002. Better handling vs the 2002. 5-speed transmissions! LSD on many of them. Better ventilation, a/c.
A great compromise between the older BMWs and the newer BMWs; a 'bridge' of sorts. More comfortable on road trips than the 02. - - - FUN.
Cons: Will distract you from your 2002, your NK sedan, your CS coupe, your Bavaria, your E28, your E36, your E46, etc., etc.
Will eat up the $$$ that you were going to put into your 2002.
Will try to take the garage space that your 2002 had exclusively reserved.