Be prepared for a firestorm of opinion here that will end with no clear consensus (including those who recommend another mfg. entirely). I think both are great units with very good receive performance and an enviable list of features, bells & whistles. Have to admit, though... that the HP-1 is simply fun to look at and use with its' very informative and colorful large LCD screen. But... that's not what you asked about so, suffice it to say that both are great receivers.... and, I personally feel that both are big improvements over earlier models.
If you're the type that likes to tinker and play with settings, the 996XT is a more hands on radio with a multitude of features that make it a superb unit for base operations. Audio output and punch is superior to the HP-1's less robust internal speaker. But..... if either is hooked up to a good amplified speaker, they each sound comparable to one another.
Best bet would be to get face to face and try each unit in advance of buying. I happen to own both units and, truth be told.... at this point.... I wouldn't want to give up either. If I were forced to choose one or the other for dedicated base use though, I personally would have to side with the 996XT for its industry leading feature set and DMA memory architecture.
PS... I wouldn't sweat the decision too much... You'll eventually buy both units anyway