Barbados or St. Lucia in late August
 

We want to take a Caribbean Anniversary trip at the end of August. Different things I've read online suggest either one of these islands is a fairly safe bet weather-wise. Want something relaxing, romantic with a flavor of the island, on the beach. All inclusive is appealing so as not to completely break the bank while still having a great trip.

Any advice on either of the 2 islands and where to stay.

You'd need to research to know if an All Inclusive really will be a money saver for you, or not. Just depends the price you have to pay for it in the first place, how much you drink, if there are other options nearby ("off property") for inexpensive eating & drinking.

That's just a general comment about AI, not specific to the islands you're asking about (never been).

You'll find All Inclusive Hotels on both islands but as suze says they come in many different price ranges so you'll have to do some basic research to determine if going to one of them won't "break your bank". By the way, the contributors on this (and other travel forums) can't make meaningful resort recommendations without knowing your actual budget in dollars. Terms like "won't break the bank", "affordable" or "not too expensive" are meaningless without a dollar point of reference.

Now, both islands have beaches and will offer a relaxing and romantic vibe so it would help if you could list other things you expect from a tropical vacation so we can help narrow down your choices. Tell us about your likes & dislikes, your ages, how long a trip you are planning, what you'd like to see and do as well as any other information you think will help us help you.

As previously said, it is hard to recommend somewhere without a price point to reference.
However, if plans are still pretty much up in the air for you then www.caribbeantraveller.com is a simple site that lays out options for you in a very simple format so you have a pretty comprehensive point of reference to see what both islands have to offer.

There are both great island choices like everyone mentioned above. However in my opinion if crystal clear beaches is important, this may mean researching Barbados a bit more both islands will have a romantic feel depending an the accommodation and activities you're interested in. If nature, lush scenery and beaches with emerald green water excites you more maybe take a look at St. Lucia.

Either island once you find an accommodation solution that suits your budget , I think would be a win win.

Good luck

Both islands are awesome and yet very different. St.lucia is very scenic with all the mountains, hospitable people, a variety of dark and white sandy beaches, volcano, waterfall and adventure where as Barbados is more of a coral island, has night life, white sandy beach and blue waters. Can't go wrong with either of them

If it is really a romantic holiday you are looking for then St. Lucia wins hands down. It was even chosen twice as the finale for the popular TV show, the Bachelor. Check it out.

Plus the bonus is the friendliness of its people.