depends where you live... I'd prefer LFS just because you can see the fish, it's behaviors, and less stress in acclimation.
I live in Los Angeles.. we have tons of LFS around with quality fish. I bought all my fish at LFS at a fraction of Liveaquaria's price and no shipping.. the ones I cannot find, my LFS can order. You won't get all the fish you want right away, but they come eventually.. (for a pair of premium Snowflake Ocellaris, web sell for $250... our LFS sell for $60)
a lot of folks here have no access to LFS beside Petco, so they depend on website orders.