I like the 4 man party. The limitation makes you think of more creative solutions to problems and perhaps your own unique character. Want to fill that rogue role but like rangers too? Play an urban ranger. It's flavourful as well. Wizards can open locks too.
In battle, you have to use your classes to their full extent. No party member is just there as a skill monkey. Makes you chosen companions matter more since you really depend on them for success. The cleric is not a healbot, it is a Cleric with a capital C.