The way I think, if you plan to DD and keep it stock, and can use what ever gas you want, then 4.0L is good, if you want off road, mod it, and want power, use only premium gas and tow alot, then get the 4.7l. for me I choose 4.0L just for DD and can use what ever gas I want and easy maintaince. if I want go fast I take my trans am out and can beat all the jeep on the road ( accept the SRT8 ^^ ) but anyway first time I buy the my jeep I Never though about going fast or mod it for off road anyway. Just get me to school/work/friend that all I need. I usually go track alot, but recently I want get away from racing/fast car, I need focus on school and something bigger to take my kid to school, that y I bough a jeep.
bottem line, I think 4.7L will make you happy if that the only car you have, for me I have my other 2 toy to make me happy ^^