Gorka 4 is an "anorak" pullover design with a quarter/half zip and a kangaroo pocket on the belly. Gorka 3 is a more traditional button up "smock" type jacket.
There are similar looking outerwears that are lighter weight but the Gorka (which means "hill" or "mountain") is by definition more heavy duty outerwear that is meant to be worn *over* your regular fatigues as a second layer. It has an effective water repelling coating that doesnt affect breathability or comfort.
If you want something lighter, the "Partizan" is what youre probably after.
http://russianoptics.net/RusCam.html
I cant do a comparison between all the different manufacturers and designs, but I have a Gorka 3 in full digital flora from SPLAV and was blown away at the quality of both the design and execution. It has pockets for knee and elbowpads, comfortable elastic cuffs and adjustable shock cords for the hood, waist etc...
The SPLAV line has a huge selection of colours and patterns you can get as well. I payed 150 US shipped from a guy in Russia who middleman'd for me since SPLAV doesnt export.