My opinion is large oval above ground. You can sink it if you want. I also have a 18x33 Johnny Weismuller (JW imprinted on the corners), the frame is really built well. I think Esther Williams is the same maker. I walk on the wall whenever I need to vacuum. I got mine for free on CL and did the work myself, the first year just cost me the liner and laser level rental. I got some seat time.
Here's a quick list:
1) Quality pool and do it yourself if possible. They are cheaper and when you are done with pool life it's easy to get rid of.
2) Hayward pump/filter because parts are easy to get - I had a no name pump and couldn't get new seals a couple years after I bought it.
3) Chlorinate with mainly liquid chlorine (straight bleach with no additives). Most of the granular or puck style chlorinators have stabilizer in them so if used constantly you will end up with too much of it.
4) Salt water gens (SWG) are nice, makes pool life quite easy. Another perk is bees don't like salt water and the water feels softer. The local honey bees really liked my pool before I added salt.
5) Buy a good/complete test kit, when the chemicals are balanced you only need to spend a few mins a day on it. With SWG (it makes the chlorine) it's a few mins a week once you have it nailed down.
6) Get a decent automatic pool vac so it does the work instead of you.
7) Depending on where you live you may want a solar cover to keep the temp nice. I need it up here, pool is about 80 right now which is pleasant.
8) Craigslist is a great place for used pool stuff if you want to save money.
9) This should be number 1, go to this site and read. So many cool setups and the pool school (top right button) is a must read.
Trouble Free Pool