Define best. If you want to be 100% sure they are free of defects and backed by warranty and fine with paying full price, then yes it is the best.
If you are willing to take a little risk and would rather pay a little less for used, then no, buying online will not be the best.
My experience has been that buying from enthusiast forums has been reliable. Only once did I get a bad set of tires that came on a wheel (they were cupped from blown shocks) but the wheels themselves were fine.