What are noticeable differences between those two engines?

The EJ18 is a 1.8 liter version of the EJ22. Looks like a smaller EJ22 basically. They also had an EJ16, but it wasn't available in the US. Notable differences are single timing belt, and distributorless ignition. I THINK the EJ18 is multivalve like the EJ22 but that I am not sure about.

Hey

 

All EJxxx engines are 16 valve either DOHC or SOHC EJ18 was usually SOHC SPFI or MPFI..we (Barbados) actually got Carbed EJ18s in '90 legacy's but I was told this I haven't actually seen this for myself..ej18s rev faster have more power rev higher. The hydraulic lash adjusters are smaller and less prone to clatter (but they still will) like all ej engines the block is a 5 main bearing design unlike ea which is 3. ej18 has an intake and exhaust port for each cylinder. ej18 is also mostly open deck in design..it isn't a bad little block God knows Subaru should'a used it in the Loyale and easily could have, but water under the bridge..

along similar lines then... are ea82's and ea82T's not overhead cam? and what exactly is the major difference between ea81 and 82 series engines?

EA81's are overhead valve, EA82's are single overhead cam. EA81's use timing gears (very durable), and EA82's use timing belts. There are many many differences, but those are the big ones.

All EA82 engines are two valves per cylender, while all EJ engines are multivalve. The EA82 has 3 main bearings while the EJ has 5. EJ is still in use after approx. 15 years and the E!82 was last used in 1994, does that tell you anything about which engine is better? HAHAHA