I can totally recommend QEEQ. I've been using rentalcars, economy car rentals, booking, others, but I've been usin QEEQ since I tried them.
They have best prices probably, and a lot of choice, plus their website is very transparent. You can usually cancelation atno cost all the way up to the pickup time.
I have even been through a loss claim during my last rental (a scratch on a car) using insurance policy which they offered and it was very quick and without any stress and hassle. Unlike other agents.