Powerful, but not really needed unless you like hauling stuff constantly. Plus, more liters = less gas millage. It would also help with off roading (if you're talking about the jeep)
1.5 to 2.4 liter 4 cylinders are my favorites, weaker, but they get the job done, if they were too weak, they wouldn't be on the market in US/Canada, europe has 1.3 liters and 1 liter engine cars, very weak, but they are 2 passenger cars.
To me, I just think the looks of the car and performance/reliability is what is important, for me, I wouldnt take a car unless it looks cool, works fine in the long run, and is cheap (like a scion XB!)
I know some people who have driven scion's for over 200k miles now with 0 problems besides tire change, oil change, and simple routine work any car has to go through.