I've got experience with both too. What Blake said is really good, I totally agree with him. My mother recently got a 99 ES and I have a 91 LS......
-The LS is more solidly build. I've inspected both and the LS parts are very heavy duty.
-The LS has more power, although it's heavier. The ES feels like it's faster but it's really not. The ES is definitely more "sporty" excellent pickup.
-The ES gets better MPG. If you're concerned about gas prices don't get an LS! Man, I hope the new hybrid LS gets better than 30 MPG!!!
-The LS is obviously bigger. And it also feels bigger when you drive it. I'm 5' 10" and it has PLENTLY of room for me!
-The LS is bigger and more expensive to keep up. It can be costly to own so beware.
-That's all I can do for now.....
Both are great cars and so it really boils down to how much you want to spend and your wants. Personally, I would find it very hard to buy anything other than an LS. However, my mother LOVES her ES and it fits her well. It's personal. If you go LS make sure to read my article on the generations so you know more about it......good luck!