i have one both and regret neither, just look for shipping when figuring price, online can be much cheaper, but some(very few) places online cna be even more brutal with shipping figured in, the cost online even with shipping can be much less
but buying locally has its advantages too, you can hand pick your pieces for size and shape, if you order online, then definitely ask about this(we got ours one time and i had a box of fist sized and smaller pieces, no prob for me, but bigger in many instances is nice), however most lfs rock is not gonna have as much if any coraline(but it will grow back), some say it does not have as much life, but we got our best selection of life from lfs rock(now we also got much more rock this way too, so it may be evenly proportionate as well)
HTH and good luck