You can walk to either, but they're a solid half-mile from the terminal. Whether that walk is "easy" will depend on your health, how much gear you have with you, how hot it is outside, and how comfortable your shoes are. I have done that walk while hauling all my scuba gear, and I was significantly sweaty by the time I got to the terminal.
I have stayed at the Beachcomber several times. It's not fancy, but the rooms have been clean, the water hot, the AC cold, and they have a great beach bar. I'm not sure what the going rates are these days (for my last two BVI trips I've flown directly to EIS), but the last time I stayed at the Beachcomber was about 50% cheaper than the Emerald Beach.
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