A round pool will be cheaper to buy and install, and it will have more sqft of floor space compared to its oval counterpart. Most people say if you have the space for a round pool go with round for those reasons.
An oval pool costs more to buy and install because of all the extra framing and parts that go into the strait wall sections. An oval pool is much less forgiving to any installation errors. What long walls must be perfectly square and level to each other and that can be tricky. If your pool builder doesn't "like" ovals I wouldn't suggest buying one from them and looking into another builder that has a better opinion about them. One nice thing about an oval pool is its much easier to build a deck up to it because of the strait wall sections you don't need to match the deck to the radius of your pool.
Then there is the subjective if the price difference doesn't bother you, and you can fit either type of pool, pick which ever shape looks better to you. I have an oval pool because my landscape limited what I could fit. I think if given the option I would put up an oval (only another size or two bigger) because I like the way it looks better than a round pool. That is purely my opinion tho you need to buy what looks best to you and your budget.
