Good question. We flew Liat from St. Martin to St. Barts. It was a quick flight...And a fun one...landing between 2 mountains/hills...a real thrill!
I haven't been to Eleuthera, but have heard wonderful things about it. It is very quiet and non-touristy. (sp)
St. Barts is beautiful!!!!!....And busy. The restaurants are fabulous and the people are very nice. If you can do it...the lodging is $$$$$, I love St. Barts. You have to rent a car here since taxis are not reliable. I can't say enough good things about the island. I found good deals at Emeraude Plage for a hotel. It is quaint and small and near the airport. The staff is excellent. There is an outdoor kitchen, which we made use of for lunch. It was neat. The bathrooms are ok in size, but are not a/c. The rooms are...k-sized bed. While it didn't compare to Eden Rock or the Carl Gustaf, it was fine.
A parent of a kid that I teach goes to Eleuthera every year and says that it is a great place. With the Euro being what it is compared to the dollar at this time, that may be a better option. I'm not sure.

Not sure if you realize, but thought I'd clarify in case. Harbour Island is a very small island off the coast of Eleuthera. Eleuthera is very un-touristy, but contains 100 miles of unexplored pink sand beaches. Harbour Island (accessible by water taxi) is tiny, and basically has one single beach. Everything is walkable, or golfcartable, or bikeable.

From what I understand, St. Barts is world class in terms of restaurants. You will not find that on Harbour Island, and definitely NOT on Eleuthera, where you basically do most of your own cooking.

Do even the most "upscale" resorts on Eleuthra not have good food? (I know the accommodations don't hold a candle to the ones on St Barts or Anguilla, but aren't there a few that are in the "high end" range?)
Also: Does anyone know which of the accommodations on either Harbour island or Eleuthra has the best snorkeling?
Finally: How does one get to Harbour Island? (Fly to Nassau and then fly or ferry to Harbour Island??)
Thanks.

You can fly to Eleuthera via Continental (for example), then take short water taxi to Harbour Island. You fly to ELH.

Or you fly to Nassau, and take a Fast Ferry to Eleuthera, which leaves early in the AM. Water taxi to Harbour.

Tippy's food is supposed to be good in Eleuthera.. near Pineapple Fields villas.

If you've been Harbour or Eleuthera, would you like to return?

Though it has been a while since I have been, my memory is that dining out is not a highlight of Eleuthera... Eleuthera is about getting fresh seafood (lobster, conch and grouper) from the fishermen and scavenging the grocery stores and roadside stands to come up with a delicious dinner that you, or a hired cook, cooks and of course about discovering beautiful beaches each with a unique character (We have had some real adventures with cars on the island.)Harbour Island seems to be much more "resort-like.
My understanding is that cuisine is excellent on St. Barts. Hopefully someone more knowledgeable can fill you in on H.I. and St. Barts and update Eleuthera if I am out of date.

Both Harbour & Eleuthera are supposed to have good snorkeling.

You'd prob. rent a car if in Eleuthera.

We stayed in Eleuthera and visited Harbour Island for a day. The food at Tippy's was excellent . . . so much so that we ate there 4 out of the 10 nights we were on island! Of course it was also convienent for us as our villa was right down the road (On The Rocks Villa . . .highly recommended) We also bought fish from the guys at the dock and grilled.

When we visited Harbour Island, we ate lunch at The Blue Bar at The Pink House Resort. It was VERY upscale and yummy and I thought the other places we drove by looked quite nice too. Think Nantucket in the Bahamas!

Poss, to answer your question about snorkeling, we've been to Eleuthera four times, and visited Harbour Island for the day each time. We've also gone to Harbour Island (quite a few years ago) and stayed. (HI has since become too $$$$ for our budget, but the snorkeling there was nonexistent anyway.) The snorkeling on Eleuthera can be anywhere from so-so to excellent, but we have usually found it to be just mediocre. There have been quite a few hurricanes pass through the area in recent years, so some of the coral etc has been destroyed or covered by sand. But there is an abundance of fish! And exploring all those beaches is why we love Eleuthera.

There are no high-end restaurants at all on Eleuthera. There are a handful on Harbour Island, but we prefer the mom-and-pop Angela's Starfish when we visit.

There are three airports on Eleuthera. ELH is the North Eleuthera airport, five mins from the water taxi to HI. GHB is the Governor's Harbour airport - in the middle of the 100 mile island. This is the airport one would use if renting a villa in the Palmetto Point area. We flew from Fort Lauderdale nonstop to GHB on Lynx Air. There are a couple more small airlines that serve FLL to GHB. These things change, so it's best to ask the villa owners for up to date info.