since i do both i think i can give you a good answer.
pak mei is harder to learn, hard to find worthy sifu and is the most different from your karate and 5 ancestors, so go with baji it is a long range to close range combat style, it has some techniques which may appear similiar to want you have already studied but is also very deep and practicle if you know what to look for, its easier to learn but this doesnt mean its anyless a great style also you already stated that your lineage will be from sifu hsu who has a great reputation.
Also the baji is slightly more external so it will be a easier transition than bak mei.
both bak mei and baji are extrmely good close range styles but baji is actually an infighting(xtrme close range) style while the piqua gives you the long range options.
Both styles use the 1,2,3 ko theory baji especially is 1 shot loaded(thou xtrmely good at it) baji is harder to recover from a failed technique than pak mei.
Do the baji but either style is an excellent choice.
Also there is alot of support for baji/piqua out there in sifu's, books etc but pak mei is very difficult to find anything.
There is no technique that speed cannot defeat......