First, the price will depend on the category and the location of the cabin. Plus, it'll depend on the exact date of the cruise. Best prices will be found in September. It also depends on whether you want to do the Eastern or Western Caribbean. You didn't mention that, so it seems like price is more important that itinerary. But they are different and offer different experiences.
With that said, the Oasis on May 11th is going to be less expensive than the Allure on May 12 for two reasons; one, the Oasis is one year older and two, the Oasis is doing the Western Caribbean.
Second, RCCL requires everyone to advertise the same cruise for the same price. Anyone offering the cruise for less is discounting and that goes against RCCL's policy, which places them in danger of loosing their credentials and obviously not someone you want to do business with. Also, keep in mind that discounters may not be available should any problems occur. Quite frankly, from personal experience, I can tell you that Cruise Compete is full of very new agents who don't know the rules, don't have alot of experience, and can't offer alot of personal advice to help make your cruise enjoyable and to avoid problems. Best advice is to look at the RCCL website and see what the price is and that is what any reputable agent will quote you.
But you definitely want to deal with a reputable agent that is a Cruise Specialist, has been doing this for several years, has alot of experience, and has personally taken many cruises. You don't want to book directly with the cruise line or some large online site that deals in quantity and not quality.
The price you're showing, does it include taxes? Does the agent charge any change fees or cancellation fees?
When comparing prices, you always want to make sure you're comparing apples to apples, so it's important to find out if they are adding taxes or not.
And lastly, keep in mind that prices change all the time. If there is a special and the price goes down, will your agent notify you and are there any fees involved in getting you the special? I know one discount website that doesn't tell you this, but if the price goes down and you ask for the special, they charge $50 per person to get you the special. Not what I would call a good deal.
Keep in mind what Warren Buffet said, "Price is what you pay. Value is what you get." Often, best price will end up costing you more in the long run and may not be the best deal.