I think the first thing you need to decide is whether you want an apple or an orange... They are totally different restaurants. Boma is a buffet and WP is table service. So, you should decide if you'd rather have table service or not. Then, start comparing the types of food offered, the location and atmosphere.
Boma and AKL are beautiful and definitely worth seeing, and I'm sure you will find something you like to eat from the many choices. My wife and I think it's all delicious, and Boma is always on our "must do" list.
Have fun and enjoy!