I think the difference between The Boiling Crab and Hot N Juicy is the authenticity. I love the seafood at both places and I think the sauces both have to offer have a unique appeal that can't quite be compared. As for the food, they are on the same level to me.
At The Boiling Crab, you can graffiti all over their walls! A cute little novelty going on, but it shows the character of the place well. Going there just makes you excited, and gives you one more thing to occupy your boredom as you wait super long in line. This puts it into comparison with Hot N Juicy where I just dread the long lines before I get to the freedom of the seafood.
The servers are also super friendly. The service here goes a long way. They smile at you, and it's a really big one at that. I really appreciate these kinds of things.
I think we do have to commend their side dishes though. I decided to order the fried calamari to calm my hunger as the food took longer for us, and it didn't feel like I was being drenched in oil. The batter was lightly coated and I could actually taste the calamari so kudos to them.