If you reset after unlocking all lands you receive permanent bonus's and an increase on the ally cap up till your fifth reset. This info is all over the guides in forums.
1st: +3% attack and spy attack 2: +3% def and spy def 3: +5% att/spy att 4: +5% def/spy def All: +50 ally slots. I've heard that there's a limit of 1000 ally slots (15 resets) but I'm not sure. Remember, you need all lands explored before reseting to get these bonuses.
But after you reset, are you start from zero. I LC already and have 20 lv4 guild. Should I reset and get the bouns?