Really most photographers can't compete with the local vendors but honestly I remember when i was trying to book for my 07' DW there were very few talented local photogs. Therefore I chose to fly in my own DW photographer and I'm very thankful I did so after seeing the resort's photographers work and being disappointed.
Just like you said, do your homework and check it out. Check out their blogs, websites, google ads, yelp basically anything with their name on it. These are going to be some of your most treasured photos for years to come! i know there are some photographers still wishing to build their portfolio in the DW area and by all means would photograph for travel fees. But i will say in most cases you do get what you pay for when it comes to photography.
Can't wait to see your photos from Diana - i'm sure they'll be wonderful!