Hi Peaches.
1) We've never met or seen anyone here who says "Gosh, I wish had made my pool smaller!" Everyone is either satisfied with the size or wants a bigger one.
2) I'm PERSONALLY biased in favor of oval over round. IMHO, I think you get a lot more useable pool area for the same volume of water. For example, a 33x18 foot pool 4' deep (water, not pool wall) will use about 15,600 gallons of water. A 33' round pool with 4' deep water will use 25,600 gallons--64% more water, requiring a bigger pump, bigger filter, and more chemicals. And more space. But that's just my opinion.