Remember, though, that you have to have a powerful enough stove to boil about 6 gallons of wort (to end up with 5 gallons). If you do that's great, but most people don't. Also, you have to have a way to cool 5 gallons of wort quickly. For only 2 gallons, that's easily done in the sink in an ice bath. That doesn't work well at all with 5 gallons though!
Overall, a full boil does improve the beer as long as you keep in mind that it should be cooled within about 20-30 minutes after it's finished boiling.